Here is a group that I got to paint up recently. The concept for this project was to do them all in a greyscale except with just a touch of color (kind of like Sin City).
I found that this technique gives me a massive amount of control over centers of interest. Simply adding the saturation to one area brings it out to the eye. It also made me consider where to put what colors (I made sure that the Inquisitor himself had the most green on him, and that none of them had too much green in places that aren't central).
This is an Ordo Xenos inquisitor along with his trusted retinue.