My opinion is that this is the result of an application of gold leaf. Typically this uses an adhesive to hold the gold leaf in place and I would expect that after the gold leaf was placed the "exposed" areas were wiped with a solvent dampened rag to remove any excess adhesive and gold leaf.
As for removal, I think a solvent such as acetone and letting it soak into the recesses should allow you to scrub everything clean with a soft brass brush. However, just to play it safe I would recommend testing that the finish won't be damaged by testing a bit of the grip frame that is covered by the grips. I would also recommend completely re-oiling the finish on the revolver after you are finished to act as a rust preventative, because acetone will remove any oils in the finish.
BTW, ALL blued finishes are oiled to provide an essential protection against rusting and WD-40 is actually a pretty good rust preventative oil. What you do is soak a paper towel with WD-40, or oil of your choice, wipe every surface so that it is "wet" with oil, let it soak in for 30 minutes or so then use clean dry paper towels to "dry" the finish. After that you can "seal" it with wax but that really isn't that essential.
