The Praetors of Orpheus use the following GW colors:
Bad Moon Yellow
Using a white-primed model, I painted a layer of Mordian Blue over the shoulder pad trim, elbow covers, chest vent (or chest eagle), knee covers, feet, and the top of the back pack. These areas were then painted with Ultramarines Blue, being careful to leave the darker color showing in the recesses. Ultramarines Blue was mixed 50/50 with Astronomican Grey to give an edge highlight to these areas. A wash of Asurmen Blue was then applied to tie the colors together and deepen the recesses.
I didn't worry much about getting the blue paint on any other areas. At this point in the process, I went and touched up any area that should not be blue with Astronomican Grey.
The white armor was given a wash of Badab Black to bring out the detail in the recesses. The armor was then given a coat of Astronomican Grey, leaving the black visible in the deepest recesses. A 50/50 mix of Astronomican Grey and Skull White was painted onto the edges and highest areas of the armor. Finally, pure Skull White was painted onto the edges and highest points of the model.
The eyes and purity seal were painted with a coat of Mechrite Red before being highlighted with Blood Red. The chest cables, vents and armor joints were painted with Charadon Granite. They were edge-highlighted with Codex Grey, before receiving a wash of Badab Black. The parchment and skull on the backpack were painted with Dheneb Stone, washed with Devlan Mud, and highlighted with Bleached Bone.
The color schemes for the Praetors of Orpheus showed them both with and without the yellow stripe on the helmet. I decided to include the yellow stripe, as I think it gives the model a bit of contrast (although it does make the model look a bit busy). The stripe was painted with a layer of Iyanden Darksun. Golden Yellow was then painted on in several layers before being edge-highlighted with Bad Moon Yellow. Devlan Mud was then watered down approximately 3:1 and painted in between the edge highlights on the top, and between the models eyes.