Well, no secret here! It's a bit obvious that this Archangel from Urban Mammoth is for the "Painting Grey" video. ;-)
There are greys tinted in every shade possible... yellow grey, purple grey, blue grey, green grey, and so on.
The idea is to show that not everything that is grey has to be Codex Grey. :-)
It was a fun exercise, and I think you will have fun with it as well!