A JavaScript / XML based colorpicker.

Click at any point in the color palette. The colorpicker checks the color at that point and assigns it to the selected colorfield.
By clicking a different colorfield, newly selected colors will be assigned to that slot, leaving the colors selected previously untouched.
You can get detailled information about the selected color(s) by holding the mouse over the colorfields - a tooltip will appear if a color is assigned.