How to change icon colors on the fly?

[Geert Delmeiren]

In this article http://www.codeproject.com/bitmap/creategrayscaleicon.asp[^] there's a function that changes an icon to a gray scale icon. I want a function to change color 1 of an icon to color 2. So, all pixels having color 1 --> changed to be of color 2. Any ideas or links? Thanks.