Understand north light before you choose
A north-facing living room never receives direct sun: its light comes from the sky, blue and constant from morning to night. It is the light of painters' studios — perfect for judging a colour, unforgiving to live with. It exaggerates everything cold in a shade and switches off everything warm.
What to avoid: pure whites such as Pure White No.1, magnificent facing south but icy facing north; bluish greys such as Mid Wedgwood No.113; and in general pale, cool-undertoned shades, which look 'dirty' for want of light to animate them.
What works: warm whites (Lots Road No.24, Holbein Chamber No.7, Sleet No.91), neutrals with a pink or yellow undertone (Fitzrovia No.26, Cadogan Stone No.59, Hoxton Grey No.72), and — often the best idea — deep colours that make the shade a quality: Brompton Road No.205, Huguenot No.49, or a night blue such as Observatory No.34.
Always test with a painted sample on two walls — the one facing the window and the one at right angles to it — and look at it at noon and in the evening under your lamps. To go further: how light changes colour, our warm whites for a dark room and our living-room ideas.