The Color Mixer is a panel with controls that allow you to define your own color using RGB or HSL components or by selecting them from a color plane.
This panel also features a predefined color palette (G) for quick access. The palette can be customized by dragging the current color from the large color field (D) on the left to the palette cells, or from one palette cell to another.
First, use the hue bar (A) to set the desired hue. Then, select a color from the Saturation-Lightness plane (B). If necessary, make fine adjustments to the color components in fields (E) or (F).