North-facing rooms get cool, indirect light all day, so colours read flatter, greyer and a touch bluer than they would on the south side of the house. LRV (Light Reflectance Value, 0 = black, 100 = white) tells you how much light a colour bounces back — and in a north-facing room that bounce-back matters more than anywhere else.
You've really got two sensible routes, and the trap is the bit in between.
Go light to maximise what little light you've got. Aim for an LRV around 55–75, and crucially pick something with warmth in it so the cool light doesn't turn it clinical. Farrow & Ball Setting Plaster, Little Greene's warmer neutrals, or a soft warm white like Benjamin Moore — these lift a dim room without going stark. Avoid cool greys here; in north light a grey with a blue base (the classic mistake) reads cold and lifeless.
Or lean in and go properly dark. North-facing rooms are where deep colours genuinely shine — LRV under 20. Think Farrow & Ball Hague Blue, Inchyra Blue or Studio Green. Because you're not fighting the light, you stop apologising for it and create something cocooning and atmospheric. Snugs, dining rooms and small north-facing studies are perfect for this.
The danger zone is LRV 30–45. Mid-tone greys, sage-y greens and mushroomy neutrals that look lovely in the showroom go muddy and dishwater in north light — not light enough to feel fresh, not deep enough to feel deliberate.
The but-what-about: LRV isn't the whole story. Undertone matters just as much. A colour at LRV 65 with a pink or yellow undertone will feel completely different from a blue-grey at the same value. Always factor both.
Practical advice: get a large sample board, paint it generously, and view it on a dull, overcast day — that's your north-facing room's worst-case lighting. If it holds up then, it'll be grand the rest of the time.