You can use this program:
http://www.tribeftw.com/downloads/TransparentIcons.exe
You can pass in as a command line switch any of these colors:
Red
Green
Blue
Black
White
Magenta
Cyan
Yellow
Or you can pass in the value of any color you can find.
For example: Red = &hff
so it would be "TransparentIcons.exe &hff"