Vlad Diaconescu shows us some of his 40k stuff. Really cool!
In his own words, Vlad used the following colors for his Grey Knights force:
Incubi Darkness as base, Kabalite Green layer for the bright green parts and biel-tan green shading. For metal parts the colors are leadbelcher and Vallejo metal washed with nuln oil and also Balthasar Gold for the golden/copper parts.