Problem:
If you want to make an colour expressed in Red Green Blue (as in the GUI Class Library) then you cannot simply subtract a value from each of the RGB values.
Resolution:
To make an RGB lighter you first need to convert and RGB value to a H S L value. This is Hue Saturation and Light, and is an alternate way of expressing a colour numerically. The L can then then be altered to lighten the colour, and then HSL can be converted back to RGB.
There are well know algorithms to do this, and I have attached a COBOL implementation to this KB Item.
Attachments:
Old KB# 7080
