Complementary colours are the pairs that sit opposite one another on the colour wheel: blue and orange, yellow and purple, red and green. When you put them side by side, each one makes the other look more intense — that's why a touch of terracotta cushion can make a blue room sing, and why green plants always look cracking against a warm pinky-red wall.
The theory is simple, but the trap is taking it too literally. Pure, saturated complementaries — bright blue against bright orange — fight each other and exhaust the eye. That works for a football kit, not a sitting room. In real homes, the trick is to knock the contrast down: pair a muted version of one with a richer hit of the other, or use one as 95% of the scheme and the other as the 5% accent.
A few pairings that actually work:
- Blue and orange/terracotta. Walls in Farrow & Ball Inchyra Blue or Stiffkey Blue, then warm it with rust, leather and terracotta accessories. The orange family is the complement that stops a deep blue feeling cold.
- Green and red. Little Greene's softer greens with a clay-pink or a muted brick red. Card Room Green by F&B with warm reddish accents is a classic.
- Yellow and purple. Trickier and best handled muted — think a soft ochre against a greyed lilac rather than primaries.
The most common "but what about" — do both colours need equal billing? No, and they shouldn't. Equal amounts of two complementaries is where rooms go wrong. Let one dominate as the backdrop and use its opposite for the things you can move: cushions, art, a single chair.
Practical advice: pick your main wall colour first, then choose accents from the opposite side of the wheel in a softer, less saturated form. Test both together on a board in the actual room — complementary contrast looks very different in north light versus evening lamplight.