Palette Shift - Help Authoring Site
If colours are not displayed correctly in your Help file it is as a result of the way the Microsoft help compiler handles colours in such applications. This phenomenon is known as 'Palette Shift'.
It is important that you make sure all your pictures use the same palette. We use paint shop pro to manipulate all our pictures, and we always save as 16 colours, never 16 million etc and always use them as 'link to file', never embed them in your document.
For more information see in our on line help manual:
Chapter 14: Help -- Using Pictures