I've just discovered a few of the brand new ceramic wall tiles in my bathroom have a faint scratch. It's certainly not deep or wide as I can just barely feel it tug if I pull my fingernails across it perpendicular to its direction. Its color is, however, light gray and hence a bit too visible against the off-white tile for my liking.
Taking the tile out is sadly out of the question, as it was professionally installed just a few months ago (long story short: I'm now quite certain the tiles were scratched upon installation, but I guess I don't deserve any better when not noticing upon job completion inspection) and my removing it would probably disturb the wet-zone membrane behind it.
So, are there any tips for what I can do to repair it? So far I've tried rubbing it with polishing leather, and I've tried to locate an enamel repair paint, but I can't find a color close enough to the shade in question.
Edit: I say the tile is in a location that's wet-zone rated. While this means I don't want to disturb the membrane, the tile is in fact rather far from any actual source of water, and any fix doesn't have to handle anything beyond the occasional light cleaning.
Here's a horrible mobile phone picture that probably doesn't help at all: