It occured to me that I had overlooked one of the obvious choices for grey handle material, Corian, or one of the other composit kitchen countertop materials. They come in a wide variety of colors, polish up like glass and make very nice grips. Some brands are tougher than others, but if you shy away from sharp edges you shouldn't have any problems.
The other idea I had was Hardybacker. It is a concreet based underlayment used for ceramic tile floors. I never tried it for grips, but if grey is what you are looking for, this stuff fits the bill!
Enjoy!
JA