Usage
Click the color picker button to activate it.
A window will appear.
This window contains a map, a slider and a colored rectangle.
In the map, the hue ranges from left to right, and the saturation ranges from top to bottom.
In the slider, the value ranges from left to right.
Set the color of the rectangle in the bottom of the window by clicking a 2D coordinate in the map, and a 1D coordinate in the slider. Then click with the left mouse button to pick the colour. A right click will cancel the pick operation.
