I have masking tape residue on multiple sections of our colored concrete. I have tried everything from pressure washing, to goo-gone, mineral oil, citrus oils, lacquer thinner, to gasoline. I stopped short of oxacilic acid. The gasoline has worked the best so far, but nowhere near even partially removing it. Both the goo-gone and gas did a well enough job of lightening the tape marks, but in turn, smeared the residue and discolored the concrete. Our concrete is not polished/smooth concrete, and we do not wish to grind it down and seal it. That would simply remove the aesthetics of what we want our concrete to look like. Any ideas?