One of the reasons I dragged my feet on these guys is because I was deciding what to do. I really like cohesive looking units, but Tzeentch units are almost always portrayed as chaotic technicolor dream units. Not really my style.
For the Horrors I decided to give them a blue scheme, since pink was already being covered by my daemonettes.
Here's a sampling of each of the troops side by side. I like to think that despite the vast difference in colors I've been able to give them a coherent look by tying them together with similar tones and accents. For instance, all of the eyes are white, metals are gold, horns/claws/teeth are bone, tongues are purple, etc.
The Flamers were a bit trickier. The problem I frequently see with their paint jobs is that their various "faces" aren't emphasized enough. I tried to take care to deepen the shadows around each head to make then stand out even more.