Grey, navy and charcoal are the cool alternative to the brown palette, and they carry the same risk: worn at similar depths they read flat. What makes them work is a visible step. A pale grey knit over a charcoal trouser has that step. A mid grey over a slightly darker grey does not. Navy is the most useful of the three because it is dark enough to anchor an outfit but has more colour in it than black, so it stops the whole thing reading as a shadow. Charcoal sits between navy and black and works with both.

Navy and charcoal are close enough that in low light they can look like a mistake, and the fix is to separate them with something clearly paler, usually a grey or a cream. The other thing to watch is undertone. Some greys lean blue and some lean brown, and a brown-leaning grey next to navy looks slightly off in a way that is hard to name. Check them together in daylight. On texture, cool neutrals benefit from a rib, a flannel or a brushed surface, because the palette has no warmth to fall back on and surface variation is what keeps it from looking severe.

We find this palette easier to wear than all black and harder to get right than brown, because the tones are so close. The single change that fixes most cool-neutral outfits is adding something clearly pale, whether a grey knit or a cream shirt, so there is a light point in the outfit. We would also be honest that navy and charcoal together only work in good light, and if you are unsure it is safer to pick one of them. If you take one thing away, it is that a cool palette needs a visible light and a visible dark, not three shades of middle.