NAME:
  setcolor
 PURPOSE:   (one line only)
  Set a 24-bit color value for plotting on 24-bit direct graphics or Postscript
 DESCRIPTION:
 CATEGORY:
  Utility
 CALLING SEQUENCE:
  value=setcolor(input)
 INPUTS:
  input - Input value.  Choices are:
           Scalar long - this is taken to be the BGR triplet,
                          example: '0000ff'xl is red.
           Byte or integer, 3-element vector - this is taken to be RGB
                          example: [0,0,255] is red.
  If the input is invalid in any way !d.n_colors-1 is returned.
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
 OUTPUTS:
  return value is the color index needed.  This is intended to be passed
    to the color keyword on many plot programs.
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
   If the display is 24-bit, the color is returned as a LONG scalar.
   If the display is Postscript, then a three color lookup table is loaded
     where 0=white, 1=your color, 2=black.  In this case the return value
     is set to 1.  To return the color to a normal setting after this
     you need to do the following manually.
   tvlct,bindgen(256),bindgen(256),bindgen(256)
     or
   loadct,0,/silent
 MODIFICATION HISTORY:
  Written by Marc W. Buie, Southwest Research Institute, 2009/01/13