32-hue horizontal gradient, full saturation, descending value vertical gradient

Hovering over a color shows its complementary color.

32-hue horizontal gradient, descending saturation vertical gradient, full value

Hovering over a color shows its complementary color.

32-hue horizontal gradient, full saturation, descending value vertical gradient, displayed in grayscale

Hovering over a color shows the original (non-grayscale) color.