Drag the sliders on Red%, Green%, and Blue% to see that color in the big circle, and to see the numeric value for that color in decimal and hexadecimal. After dragging a slider, you can change its value up or down by 1 with the arrow keys. Press 'd' or 'h' to enter the decimal or hexadecimal RGB value for a color.
I got the idea for using pen to efficiently draw the circle, from a nice robot-arm program by Yllie.
