Colors That Clash

This is our own rule, not an upstream citation — the Rams review has no bullet for it, and we previously mislabelled it as one. The practical test is not "do these two hues look nice together" but "where did this hue come from": a palette generated in a perceptual space (OKLCH is the practical one) gives you hues at matched lightness and chroma, so a warning next to a success next to a primary read as members of one family instead of three separate accidents.

Ad-hoc picks fail in a specific way — they collide at the same lightness, so the eye cannot tell which one is meant to be louder. Choose the relationship (analogous, complementary, triadic) once, encode it as tokens, and let components consume tokens only.