Chagall Reference   Select colour         12.5.93
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   For selecting colours you use a dialog box that
   always appears when you click on a colour patch.
   In the present Chagall version colour selection
   is based on the RGB or, if preferred, CMY colour
   model:

   The colour square at top left of this dialog box
   represents a section through the cubic RGB or CMY 
   colour-space. The location of this section will
   be pre-set by the Blue intensity (using the 
   corresponding slider), so that by clicking in the
   colour square you can alter the Red and Green
   components; for altering the Blue component you 
   have to resort to the Blue slider, however.

   Incidentally, a double-click in the colour square
   selects a colour and then automatically quits the
   dialog.

   The above procedure is well suited for picking a
   hue quickly when absolute precision is not needed.

   The upright rectangle to the right of the colour
   square shows the currently selected colour, which 
   can be altered either by selecting a new colour
   from the colour square or by using the sliders. 
   For even greater precision, you can click on the
   numerical readout next to a slider, clear the
   resultant 'value' box with <Esc> and type in a
   new value which will take effect as soon as you
   press <Return> or <Enter>.

   When modifying monochrome or halftone pictures
   the colour selector will be slightly different:
   The colour square will have a grey gradient from
   top to bottom, and there will be only a single
   slider (for black).

