1.Slider representing “hue” of the color.
2.The black circle shows currently selected color. Different color can be picked by clicking left mouse button.
3.Sets foreground color to black and background color to white.
4.Represents foreground color. Foreground color is used by paint tools. If this rectangle is clicked by left mouse button then color dialog will appear.
5.This button switches background and foreground colors.
6.Represents background color. Background color is used by eraser tool (only when mask is edited) or by gradient tool. If this rectangle is clicked by left mouse button then color dialog will appear.
7.The RGB represents Red, Green and Blue channels of currently selected color. Channel values can be edited manually.