Color2Index
returns the “reference constant” of a control
Color2Index uses the list of search procedures in the current device record to come up with the closest possible match for a requested RGBColor.
rgb is the absolute color requested by the application Returns: a 4-byte long; a padded pixel value filled out with zeros in the high word.
Notes: Color2Index is a color conversion function that returns a padded pixel value with zeros in the high word. Because the colorSpec.value field too
short by half, the low word of Color2Index's result is truncated to fit into the colorSpec. The .value field of a PixMap would be the low-order word of this index.
Don't have your application call this function from a custom search
procedure.