Click a swatch's lock to keep it, then shuffle to re-mine the rest. Click anywhere on the image to stake a manual claim from that exact pixel.
WCAG ratio
A contrast ratio is how far apart two colours are in lightness. Identical colours are 1:1. Black on white is 21:1, the furthest you can get.
WCAG is the accessibility standard most of the web is held to. It asks for 4.5:1 behind normal text and 3:1 for large text, icons and borders. Those are the numbers this panel checks.
It matters away from a good monitor: low vision, a phone in sunlight, a cheap screen, tired eyes. A pairing that looks fine here can be unreadable there. That is what bears weight means — it will hold text. Decorative only means use it, just not under words.