The colours that tie the different bands of the cult together are black, purple and yellow. Two or all three of those colors appear in almost all models of the cult. Check the earlier entires
Undercoating with spray. First Grey Seer all over followed by Wraith Bone sprayed just from above.
This gives a bit deeper shades than using just Wraith Bone.
First colors on. Magos Purple for psykers shirt and
Talassar Blue for beastman skin.
Spyker´s pants and beastman´s horns were done with Nazdreg Yellow.
Guilliman Flesh for hands and face of the psyker.
Leather parts using Black Templar.
I use Leadbelcher for metal parts and treat them with Agrax Earth Shade.
Some Agrax is added to areas of deepers shadows too.
Wyldwood is used for weapons shafts etc.
Finally I highlight skin and fur parts with mixture of contrast paint and normal white diluted heavily with medium. I try to add several thi layers to make sort of gradual highlights.
For last I traet the base with Snakebite Leather, pva glue and some flock.
Here´s another guide I did for speed painting desert themed Imperial Guard.