Even rotations throughout the HSL colorspace produce incorrect complements

[B3rry]

Evenly rotating around the H in an HSL color model will not produce true complementary colors.

Light based color models have equidistant Red 0°, Green 120°, and Blue 240° values. In contrast, pigment-based color models (on which the foundations of color theory are derived) have equidistant Red, Yellow, and Blue values.

A quick test shows that rotating 180° from a “pure” blue results in the following: (240°+(360/2))%360)=60°. The output of this transformation is a “pure” yellow: a non-complement. With orange, 30°, being the correct complementary value.

The proper method for transforming a light-based color into it's pigment-based complement (and respective derivative harmonies) is to divide the distribution of values evenly between the primary points of 0°, 60°, and 240°. This means you should produce three relational formulae based on the proportional offset, and rotate through them once the primary thresholds are met.