Buy the navy blazer. Just not the navy trousers.

Few pieces of advice in classic menswear are as unanimous as this one: when you buy your first suit, buy a blue one. Yes, there are edge cases and exceptions, but the answer is navy pretty much across the board. The only serious alternative is the charcoal suit, and we can leave black out of it as long as we're not talking about evening wear. With jackets it gets a shade less clear-cut, season and occasion come into it, but even there the navy blazer is one of the first things you reach for, and hardly anyone would seriously argue.

And then you get to trousers, and the advice flips into its exact opposite. Navy trousers are the first thing I'd talk anyone out of. Same colour, the safest tip there is in one place and the exact opposite in the other. If it were really down to the colour, that couldn't happen.

So we're clear from the start: nothing here is forbidden. This isn't a rule you're not allowed to break, it's a case for the easy route over the brute force one. I'm also not claiming there's no look at all in which navy trousers work. There probably is one. I'm only claiming that the alternatives are almost always easier and better, and that this rule is good enough to hold on to. You don't have to avoid navy trousers. But if you wear them, you're making life harder for yourself than it needs to be.

You may know the feeling from the other side too. You've got dressed, on paper it all works, trousers, shirt and jacket fit, every colour is fine on its own, and it still looks somehow wrong. You just can't put your finger on it. What's happened is this: your eye picked up something in half a second that your head has no explanation for, or simply no words for. It happens to me too sometimes, and that's exactly why I started looking for the terms that would actually pin it down. That's what this is about.

Navy is rightly the favourite

Let's quickly note why the reflex towards blue is so strong, because the reflex isn't wrong. Navy is probably the most popular colour in all of classic menswear, and for good reasons. A navy suit almost always looks a touch better than its grey brother, and that's why the standard answer to “what do I start with” is the navy suit, and the answer to “which single jacket do I need” is the navy blazer.

The same problem would apply to charcoal, incidentally. The rule I'm coming to applies to the grey suit just as much. It's only that hardly anyone is tempted to wear the charcoal jacket on its own, because the navy blazer is the piece and the charcoal jacket is the poor relation at best, maybe as a grey herringbone. Which already tells you something: it isn't the colour navy that sets the trap, it's the sheer number of navy suit trousers out there. Almost everyone has a pair, so almost everyone wants to wear them on their own at some point.

Let's look at the cornerstones of menswear, and above all at the point where the logic suddenly falls apart. Navy blazer, mid-grey trousers, light shirt, darker tie: that's the universal menswear uniform. Navy blazer, beige trousers, light shirt and a tie of your choosing: the California tuxedo, which everyone has seen and everyone enjoys wearing. Navy blazer, olive trousers: still outstanding as far as I'm concerned, a shade more relaxed maybe, but perfectly presentable anywhere. Anyone who claims green and blue don't go together has no idea.

Now flip one of those outfits round and put the navy trousers at the bottom as your starting point. The colours are the same, they've only moved from top to bottom, and all of a sudden it's heavy going. You start tinkering, hunting for the jacket that still works with them, and you notice the easy hits have gone. If it were really down to the colour, that couldn't happen, the colours are all still there.

This is where a claim comes in that I've been making for a long time: the neutrals you really need in trousers are mid grey, beige (and I'm generous enough to include off-white) and olive. With those three you put together 95% of your outfits. Navy doesn't belong in that group! With beige you do have to watch the undertones, because too much red quickly makes the colour too warm. How warm earth tones work with each other is a subject of its own that I'll come to another time, because plenty of people mess it up for exactly that reason: they think you can throw any browns together.

It isn't the colour, it's the direction

If the colours are the same in both versions and one of them still looks better, there has to be a second axis making the difference. And that lies in the direction of the contrast.

Blocks of dark colour have something like a weight to them. The usual name for this is visual weight, and that almost covers it, but it goes further, because it takes in texture, pattern, volume and sheen as well. For now I want to keep this deliberately to light against dark, so I'm calling that one part tonal gravity. It isn't an established term, it's a deliberate narrowing, and that narrowing is the whole point here. The other axis, saturation and sheen, I'm keeping back for now, we'll need it later. And there's a third factor, one you won't find in your wardrobe: your own head, your hair, beard and skin. That's a subject of its own, but I'll touch on it below when we get to the black tie.

Light against dark has a kind of gravity. And it helps if that gravity pulls upwards, towards your face, rather than down towards your legs. Perhaps you've noticed something was off in the mirror but couldn't describe what. The weight pulls down when you want the eye to stay up.

The standard is dark, light, dark: a dark jacket, a light shirt, a dark tie. There is a clear contrast between jacket and shirt, and another between shirt and tie. These contrasts sit in the upper part of the outfit, across the chest and up towards the face.

A light jacket makes this combination harder. Over a shirt that's also light, you have less contrast to begin with. A dark tie brings it back between shirt and tie, but the distribution is different from what you get with a dark jacket. With a beige jacket over a white shirt, for example, I'd be more inclined to choose a coloured tie, perhaps a red one, than automatically reach for the darkest.

“Then I'll just skip the contrast”

You can raise objections to this description, and the first one goes: if the dark has to be at the top, I'll get around the whole thing by making no contrast at all and wearing dark on dark.

You can do that, except then you've got a suit. And a suit you pass off as two separate pieces is still a suit and not an outfit built from separates. You cancel the gravity by spreading it evenly over the whole outfit. It's a trick, and it works, but it doesn't disprove the concept, it confirms it. A single tone from top to bottom produces no jump, so there's no direction left that could tip.

And here you get the case where navy trousers really do go wrong, so clearly that nobody argues with it. Solve the contrast problem by putting a black or charcoal jacket with the navy trousers and you land straight in a different trap. It then looks as though you reached into the wardrobe in a still-dark bedroom in the morning, went for the navy suit and came away with the wrong jacket. Two dark tones that almost match, but not quite, blur into each other, and it reads as a failed attempt to match the colour. That's the real danger zone with dark trousers: not the clear contrast, the near miss.

That also shows you there are two axes in play. The first is the strength of the contrast. If it's weak, the direction is free. The second is the direction, and it only counts once the contrast gets strong. Dark tones also stack worse than light ones, which you may know from old displays, where large dark areas quickly show edges and banding, while light gradients break down more cleanly into many fine steps. In cloth the technical side is a different thing and I'm not out to prove anything with it, but the perception runs along similar lines: light colours leave more room for differentiation, dark ones less.

One side note, because it rounds out the picture. The Japanese approach is to budget colour, and the rule is two colours in an outfit, three at a push. White, grey and black count as neutral there, they don't go on the colour budget, and an outfit sticks to a few colours plus those neutrals. That's a different question from ours: it's about how many colours you wear, not about where the dark sits. Which is why the budget protects nobody from navy trousers. Navy trousers under a mid-grey jacket are perfectly clean on the budget and still go wrong, because gravity is a matter of lightness, not of the number of colours.

The people who want to make it work anyway

Before anyone comes at me with counterexamples where the navy trousers work beautifully: they exist, and they're worth looking at, because they're where you really come to understand the rule. Simon Crompton, for one, wears navy trousers outside a suit again and again.

In one case he pairs them with a grey jacket and a grey shirt. Put the exact reverse next to it and the easier, better solution is right there. Crompton can carry it off, no question at all. The only question is why you'd go to the trouble when there's an easier way.

Another time it's a white shirt with a white and blue striped seersucker jacket. The contrast rule has a weaker grip here anyway, because the outfit is close to monochrome, and monochrome looks work differently in perception. Four different shades of blue can sit next to each other because it's all blue. Four actual colours next to each other would be a good deal harder, if not impossible. That's a legitimate route, and even so you can feel the weight tending downwards here too. The stripes hold it in balance, but they don't quite cancel it.

Now to the examples that were meant as a challenge, meaning someone publicly set out to force navy trousers to work.

There's the bright red, high-shine tie with royal blue stripes, one of the loudest I've ever seen. And what is happening here is different from everything up to now. The red doesn't rescue the look through lightness, it does it through the second axis I parked earlier: saturation and sheen. Call it chromatic weight, to keep it apart from tonal gravity. The deep, glossy red wins the complementary contrast against the blue, tears that second axis open and pulls the eye up to the neck, and an earthy jacket picks the red up as well. It genuinely works. It's just loud, and it doesn't solve the actual problem, it shouts it down. That's brute force in its purest form: you make so much noise up top that nobody looks at the trousers any more.

The next look is more interesting, because it doesn't trick its way out at all, it follows the rule cleanly. A black tie is darker than the navy trousers and brings the weight all the way back up, exactly where it belongs. And I have to be honest here: until recently I was convinced black ties ought to be banned outright. While I was working on this piece, Daniel of @ivy_archive_munich happened to run a story on precisely that, and he changed my mind. His argument: black is a true neutral, with no colour value of its own and no undertones. A black knit tie, specifically the matte knit and not the shiny one, is therefore a safe bet. Whatever blazer and whatever coloured shirt you go with, it doesn't clash with anything. That fits the achromatic logic of classic Ivy, which the Japanese in particular have codified down to the last detail: black doesn't go on the budget, but it very much works within the contrast family.

Daniel goes further still. “Black is just very, very underrated,” he says, and his favourite piece of evidence is Take Ivy, the picture book of the whole style, in which the black tie turns up as a standard again and again. His test is the capsule wardrobe test: “If you only had the budget for a single tie, technically I'd always take the black one, because it has no saturation of its own, no hue of its own, no warm tone.” Even with a blue shirt, the standard in Ivy style, he reckons you're better off with black than with blue. I take his point, even if in the end I'd rather wear a tie with a bit more character. But that's another story.

And here's the point where I don't want to hedge: this look works. The black tie brings the weight up in line with the rule, that isn't cheating, that's the rule in action. That outfit, grey jacket, white shirt, black tie and navy trousers, ends up containing only a single real colour, the blue. Nicely done. It's just that you've used up a tie whose only job was to make up for a problem you brought on yourself with the trousers in the first place. With grey or beige trousers you'd have had free rein up top and the tie free for anything else. That's the whole difference: not works or doesn't work, but given to you or worked for.

And there's something we need to include here that no rule about combining clothes accounts for: your head. Dark hair, a dark beard, dark skin: that's a built-in block of darkness just above the collar. If you have it, you already satisfy the rule before you've put on a single piece of clothing.

I keep seeing Ethan Wong, for example, in light jackets over dark trousers, and on him it works because his jet-black hair and black moustache already provide the anchor at the top that he doesn't need to find in his clothes. Someone with less contrast in their face copies the look and wonders why it doesn't work, or brings that anchor back with a dark tie.

The bottom line is simple. It isn't that it never works, I'll happily grant that. It's that the alternatives are always better and easier. Everyone has a blue suit, and that's fine. The trouble is you then think you have to wear those trousers on their own as well, and you make life hard for yourself. Go to the neutrals instead and you have free rein up top, because your navy jacket goes with everything. So why go to the trouble?

Postscript: navy gives you brown

Since this piece went online, the objection has come in: navy trousers do work. The remarkable thing about it is that everyone who came to me with it presented the same solution. A fairly warm brown up top.

Which is exactly the point.

I wrote earlier that I'm not claiming there's no look in which navy trousers work. What I'm claiming is that they aren't one of the pairs of trousers you build your outfits around. When the same objection always comes with the same single answer, that isn't a refutation, it's confirmation. Beige, grey and olive give you the whole wardrobe. Navy gives you brown.

Why the pairing works is still interesting, because it isn't running on lightness. A warm brown is often not darker at all than the navy trousers below it. Visual weight is more than light against dark, warmth and intensity come into it, and that's exactly the axis I set aside at the beginning. Against a cold, very dark navy, a mid brown that brings some warmth with it simply has a bit more presence. That can be enough.

And there you have the difference from the bright red tie earlier. That one wins on the same axis, but it wins on volume, it shouts the problem down. The warm brown wins quietly.

The case that seems to break the rule

So far, so clear. Now for a small puzzle that seems to overturn the whole weight story.

Take the logic all the way through. You have the dark trousers, so you need a light jacket on top for any contrast to happen at all. Add a light shirt to that and there's no contrast left between shirt and jacket, so the logical move is a dark shirt. And that, unfortunately, looks worse again, because now there's nothing light left right by the face. There is still contrast between jacket and shirt, now with dark on the inside and light on the outside. Then there's the contrast between the light jacket and dark trousers further down. So it isn't that dark always has to go on the outside. The black tie from earlier sits on the inside and works because the white collar stays by the face. A dark shirt removes exactly that.

The one exception is light summer tones, linen, an open collar, light tones at every layer, where low contrast is a deliberate part of the look. A cream jacket over darker trousers can work perfectly well there. But that's a conscious, tonal decision for that particular mood, not an effortless default you pull out of the wardrobe every morning.

There is one case, though, that ought to be bad by the same logic and still looks good: a pale blue chambray shirt under an off-white jacket. At first glance you think the blue is obviously darker than the beige, so it should go wrong. It doesn't, and the reason is a lovely one. And this isn't a side issue: without that mechanism you apply the rule wrongly, because you're too quick to take a blue striped or melange shirt for a dark one and rule it out, when in truth it reads as light.

A chambray is made from one white yarn and one indigo yarn. At a distance your eye can't resolve the two. It does register that there's blue there, but it averages the intensity, and averaging pale blue with white lands you at an extremely light blue that has practically no contrast left against an off-white. On top of that, chambray has a rougher texture, which absorbs the light differently and makes the colour look even more desaturated than it is. Put something genuinely dark and solid under the beige instead, dark blue, dark red, and it stops working straight away.

That is the proof that it isn't only down to lightness, it's down to the structure as well. A solid pale blue Oxford would look considerably worse here than a white and blue one, even though both are similarly light. With stronger colours, solid shirts are often a worse choice than two-colour ones, which do the same thing optically but are easier on the eye because the structure is broken up. Stripes do the same. There are so many striped shirts around not only because stripes are a simple weave, but because the white in between takes the edge off the colour's contrast and makes it wearable.

The mechanism behind it isn't a matter of taste, it has a name: optical or partitive mixing. Two fine yarns genuinely desaturate each other as soon as the eye can no longer separate them. It's basically like a screen whose pixels mix the colours because you can no longer resolve them. The same principle sits behind Seurat's pointillism and the halftone screen of four-colour printing.

The tipping point is the multistripe. With every extra colour, and every stronger one, it gets louder, at some stage the eye resolves the stripes separately again, and the soft mixture turns into hard contrast. Which is why there are so few successful multistripe shirts. The ones I own that do work stick exactly to the exception: one is pink, pale blue and white, and pink and pale blue are heavily desaturated complementaries. The other is pale blue with black and white, and black and white are neutrals, so strictly speaking it isn't a real multistripe at all.

There are exceptions, of course. A solid olive shirt can look very cool, that's more of an outdoor look. I wanted a solid yellow shirt for a long time and gave it an honest try, but that block of saturated yellow was simply unpleasant to my eye. A yellow stripe is probably the answer. A block of red or black, on the other hand, rarely makes sense.

Two questions instead of fifty colour pairs

Perhaps you've looked at an outfit and seen that something was off without being able to say why. Now you can check whether it's down to the distribution of light and dark, and make a deliberate change. The rule also helps when you're putting an outfit together: you can judge what's likely to look good and what will make things harder for you.

With jeans and a T-shirt, the rule barely comes into play. It becomes important when you combine and layer several pieces. On your lower half, you have trousers and shoes; you don't layer the trousers themselves. On your upper half, you might have a shirt, tie, jacket, scarf and coat, with three, four or five pieces visible at once. They have to work with one another and with the trousers. So it's not just a question of whether a top goes with a pair of trousers, but also of how the light and dark pieces on your upper half relate to one another.

You don't have to learn fifty colour combinations by heart for this. The first step only looks at the contrast, and two questions are enough. Is there a strong light-to-dark contrast? And if there is, does the dark sit at the top? And you only need to ask yourself the third question once: how much darkness do you already bring to the outfit yourself? That's a surprisingly reliable rule for an outfit that comes off.

In the end classic menswear comes back to the same five colours again and again, but the nuances decide it, and that isn't splitting hairs. For trousers that means beige, grey and olive, and navy isn't part of it, with the one exception from above. As long as your beige and your olive don't have undertones that are too warm and you keep the contrast pointing up, they work with just about any jacket colour you can think of. Which gives you free rein up top.

And this isn't a private quirk of mine. Go through the lists of which trousers to buy first, all the capsule wardrobe and essentials guides you can't avoid online. Grey is on there. Tan or beige is on there. Sometimes olive, sometimes cream. Navy isn't on a single one of them. Nobody bans navy trousers out loud, they just never turn up when it comes to the solid first pieces. That gap says more than any rule I could write down.

The finer things, complementary colours and real colourfulness, are a smaller subject of their own, and most of the time that only applies to accessories anyway, maybe to a Shetland jumper. Your real colour accents usually come from the pocket square and the tie, rarely from the shirt. But that's a story for another time.