To help prevent voter fraud, not help fraud, I assume.
I don’t understand how wearing red helps.
My best guess: photos of red-clad Trump voters would give an estimate of his true vote count in a way that is publicly visible and could be documented by photos. If there are significantly less Trump votes than the photos show, it would suggest (but not prove) vote fraud.
Its an idea, but not one I’m sure would work, and depending on one’s precinct, maybe not a good one at all.