The color map box displays color maps, which are set of colors that share a value for one of their color channel.
Any of the color maps square can be clicked to update the current color.
Buttons let you choose the kind of color map to display.
map of colors with same red level.
map of colors with same green level.
map of colors with same blue level.
map of colors with same hue.
map of colors with same lightness.
map of colors with same saturation.
map of colors with same cyan level.
map of colors with same magenta level.
map of colors with same yellow level.
gray scale: this is a special color map, as it never changes, whatever the current color is.When you unlink the Color map box, a slider appears in front of the color map title, so you can adjust the constant level.
The color map can have a more or less fine grid: you can choose the definition here.