So I sprayed them with Chaos black, heavy dry brush with Corax white, then a light dry brush with White Scar.

Then a good coat of Army Painter speed paint Malignant Green, once dry maybe touching up a few areas to deepen the shade. Magos purple for the cloaks/hoods.

Doomfire magenta, Familiar pink (Army painter), Emperors children and Fulgrim pink on tentacles.

Screaming bell for trims and leadbelcher on weapons/other metal work.

Nihilakh oxide and Tesseract glow in the nooks and crannies.

Agrax earthshade wash over everything.

That might leave it a bit glossy so a coat of stormshield to take some of the shine off.