With the Officer of the Fleet, it is the first time I tried painting a white outfit. I used Codex Grey as the base coat, and then painted Skull White over it. I washed it with more Codex Grey that I thinned down with water, probably a 60 (water)/40 (paint) mix. Finally, I highlighted it with more Skull White. It came out nice.
With the Astropath's robe, I base coated it with Catachan Green and highlighted it with Camo Green. Then, I washed it with Orc Flesh Wash (not watered down). That is all I did and I really like how it came out.