I am using rubber cement to partially cover my print (FB Matte) so that when I tone it won't affect the area with the cement.

A big problem is that some of my rubber cementing is very intricate and the material being basically milky clear and when dried clear, it's hard to spot a thin area or area that didn't get covered. I'd like to color the rubber cement but with a material that won't color the paper that is being applied to. I'm using brush and toothpick to do this and a magnifier but I'm still missing spots.

Can anyone think of a coloring material that would do it? I'm thinking any kind of dye wouldn't work but fine colored powder that is NOT soluble might. Problem is, I don't know what that might be.