* This calculates a color. If value is equal to min the returned color is
* minColor, if value is equal to max the returned color is maxColor,
* otherwise a color 'proportional' to value is returned.
* This calculates a color. If value is equal to min the returned color is
* minColor, if value is equal to max the returned color is maxColor,
* otherwise a color 'proportional' to value is returned.