Hi !
That`s my new pj and it have a guide with steps and photos of process, which was big part of work.
Full tutorial You can find in Issue 7 of Figure Painter Magazine
at http://www.figurepaintermagazine.co.uk/
If You like my tutorial and want me to write more, then let me know.

This work is high-class commission painting for the game.

Here is a little fragment about colors choice from my guide.
Note that text in magzine was redacted because of my poor english,
so there can be insignificant difference.

Colors choice idea.
In my vision, there two colors which fit these beast perfectly - black and red.
Black, on this sculpt, can create allusions on evil, massacre, absorbtion.
Red gives violence, blood-thirstiness, high energy.
But I really bored of black, its most popular and usual color .
So I have maked choice to replace black with grey.
Grey gives more tactical minded look, ancient spirit,loneliness, hidden despair.
Red with grey looks more elegant and lightweighted.
And little dust Yellow glazes in addition, for more realistic view.
Also in nature rhinoceros and elephant have most similiar look to these chaos beast.(Among big sized animals)
And they both are grey.
Another point is that this beast extremely overloaded with elements and has complicated surface texture (all these crinkles, scales and horns) so simple color choice like grey- red- yellow will make some balance.