The color picker interface allows the user to selected a color for the current selected element.
On the top you can choose between the inner color and the border color, both selection are only available for figures.
The color picker main interface is the HSB or RGB interface where you can select the color depending on your preferences. In the HSB you can adjusts the brightness. In the HSB and RGB you can also set the alpha value, between 0 and 100%.
At the bottom of the interface, you have predefined color pallets.