Well...that might happen if their skin shows through for a period of time, since palominos usually have dark skin? I don't have personal experience with greying palominos though, I just know that the way grey works is that more and more white hairs come in over time and replace the pigmented ones. But I also have little experience with dilutions, so as I think Chandab mentioned upthread, "weird things can happen" if dilution genes are combined with grey too.
For whatever reason minis seem to have a plethora of color things going on and sometimes you end up with a silver dapple grey pinto appaloosa kind of situation that is just way too much for my pea brain to digest. Luckily my guy is just a silver bay pinto, that I can wrap my mind around.