My first reaction when I opened up the box was that they had shipped me the 610 instead of the smaller 615. It is still a very big knife, to the point where I wouldn't want it any bigger for pocket carrying.
Check out this thread from ar15.com: http://ar15.com/forums/topic.html?b=6&f=19&t=218202&page=1. The poster did an excellent job doing a MC paint job on his M4. He also explains how he did it and includes pictures. Enjoy!