The G-10 Grips are impervious to the Rem oil or other lubricants, as a matter of fact the oil may enhance the color.
One of the first things Karl did after my new VZ Grips were installed on my R-9 was to wipe both pistol and grips with oil. It really brought out the grips.
I'd look elsewhere as to a problem with discoloration to the grip.Maybe it is a pool of oil stuck in the grip screw hole.