Grimstonefire:
Although they are quite far down my list of things to buy, I quite like the idea of collecting some horrors.
After looking at those plastics, what I’ve been wondering is how you could paint them to actually look horrifying, and what I decided was that painting them a bit like tyranids may be the answer.
Mainly black, but with some hints of purple and pink.
Thoughts?
Thommy H:
Paint them like fire, with reverse higlighting. You could do different colours, but all going from white in the recesses to black on the raised areas.
Baggronor:
Perhaps something with metallics? My mate has been experimenting with mixing metallics into his colour schemes with some surprising results; his metallic sheened Cold One is quite cool (sparkly greens).
Or maybe some directional lighting effects; glowing eyes, flaming arms, etc? As they are Plastic, you could even try melting them into each other :o
Xander:
I like your black idea, like oil with light hitting it, creating a bunch of other colours on its shiny surface.
Loki:
The black idea gets my vote as well sounds cool 
Kered:
I would say black and an electric blue.
Ishkur Cinderhat:
I’d go with several different Citadel washes - painted somewhat overlapping to create different shades on each model and create a truly chaotically coloured unit that still has a very unified scheme.
If that makes any sense to you, that is. g
AGPO:
If you’ve got the time, I’d suggest giving each one an individual scheme. Not only will each model be truly unique, but there’s two other advantages:
1) it allows you to experiment with new techniques
2) such a varied unit is very Tzeentchian