Here's the honest truth, mate: dark colours making a room feel smaller is a myth that's been repeated so often people treat it as gospel. It isn't.
What actually happens is this. A pale colour shows you exactly where the walls are — every corner, every edge, every box of a room. A deep colour does the opposite. It softens the boundaries, the corners recede into shadow, and you stop being able to read precisely where the room stops. That ambiguity reads as depth, not confinement. Small rooms — box bedrooms, downstairs loos, north-facing snugs — often work beautifully in dark colours because they were never going to feel airy and palatial anyway, so you lean into cosy instead.
Where it goes wrong is half-measures. A dark wall with bright white skirting, white ceiling and a pale carpet creates hard lines that chop the room up and emphasise how small it is. The trick is to commit. Take the colour up over the ceiling, paint the woodwork the same shade or a close tonal match, and let the whole thing wrap around you. That's when a small dark room sings.
For a properly enveloping snug or study, Farrow & Ball Hague Blue or Inchyra Blue are cracking — deep but not flat, with real colour movement. For something warmer and softer, Farrow & Ball Mole's Breath or Little Greene in a deep muted tone gives you cosy without going pitch black. If you want drama in a tiny loo, Studio Green or Mylands Marble Arch No.82 done floor to ceiling is genuinely lovely.
The one practical thing that matters more than colour depth: lighting. A dark room needs decent layered light — lamps, not just a single ceiling pendant — and warm bulbs around 2700K. Get that right and the colour glows. Get it wrong and yes, it'll feel like a cave.
So don't let the myth talk you out of a colour you love. Commit to it properly, sort the lighting, and a small dark room will feel like the best room in the house.