A base colour plus the two colours next to its complementary opposite, rather than the exact opposite itself.
A base hue plus the two hues at roughly ±150° from it (i.e. adjacent to the 180° complementary point).
Split-complementary is often confused with a plain complementary pairing — the 'split' specifically means two near-opposite hues, not one exact opposite.
Blue paired with yellow-orange and red-orange (rather than plain orange) is a split-complementary scheme.
Split-complementary schemes give much of a complementary pairing's contrast with slightly less visual tension.
The scheme is a base hue plus the two hues a fixed angle either side of its complement. Colourwise uses 30°, which places the pair 150° and 210° from the base. A narrower split approaches a plain complementary pair, and a split of 60° turns the scheme into a triad, so the angle chosen decides how much opposition is left.
| Colour | HSL hue | ΔE00 from Royal blue | Contrast with Royal blue |
|---|---|---|---|
| Royal Blue #4169e1 | 225° | 0.0 | 1.00:1 |
| Direct complement #e1b941 | 45° | 65.7 | 2.59:1 |
| Split, 150° on #e16941 | 15° | 46.6 | 1.45:1 |
| Split, 210° on #b9e141 | 75° | 72.9 | 3.21:1 |
The two split hues, #e16941 and #b9e141, are 54.1 ΔE00 from each other, so the scheme has three distinguishable colours where a complementary pair has two. Against Royal blue they give contrast ratios of 1.45:1 and 3.21:1, compared with 2.59:1 for the direct complement.
How this was calculated: Colourwise's split-complementary rule takes the hues 30° either side of the complement, that is 150° and 210° round the HSL wheel from the base.
An interface needs a main colour, a secondary accent and a warning colour that do not look alike.
Picking the two accents from either side of the complement gives hues that are distinct from the base and from each other, but one of them often lands on a red or orange that users read as an error. Check the split hues against the meanings the product already assigns to colour.