Hue memory
Study the swatch for five seconds. It hides; match the hue with the picker (saturation/lightness of the swatch are random each round). Closer hue earns more points. Five rounds — your average updates the benchmark hub.
Each swatch picks a random hue, saturation, and lightness so you see colors across the whole space. Your score still uses hue distance only. Native color picker varies by browser and OS.