I've tried to imitate some V-Ray materials by Grant Warwick lately. Didn't get very far, but i'm really happy with this result. Fortunately it's not too close to the original, so it must not be marked as fan art.
Of course you can plug in any colour, but you can also use the colour shift value (goes between -1000 ans 1000) which allows very subtle colour changes. The HDR I used for the first render is not included.