xPALETTE L T W H

  This is a palette gadget from which you can choose colors.

  Every time a color is selected, the palette will "happen" and the
  internal variables COLOR.R, COLOR.G, COLOR.B, COLOR.NUM, COLOR.TOTAL
  will contain the R G B values, the color number and the total number
  of colors. 

  Look at the Internal Variables for more info.

  The number of colors is taken from the screen that the
  window with the palette gadget will open on.

  You can update a palette by choosing another color :
  > update GuiName gadID NewColorNumber

  Look at the guis:tools/palette.gc gui to see an example