Near-black plum, deep aubergine, royal purple, and Rebecca Purple create the strongest contrast on white, ranging from 17.03:1 down to 8.41:1.
Two lighter purples reach 6.54:1 and 5.66:1, still above the WCAG AA minimum for normal text on pure white. Those measurements belong to these exact opaque pairs and must be recalculated if either side changes.
