i finally just decided to go for it. regular ol' paint. not even gloss.
it took two coats. i painted them the same color as the cabinets (but went with satin instead of flat) using a brush for the grout and a small foam roller for the tiles.
wish i would've done it a long time ago!!
it's so much brighter now!!
it's flawless and smooth and looks like the tiles were made that way. if you're thinking about doing it, just do it. Nike®