Question about red evolutions further upgrades

I know that icons can't be evolved, or founders evos can't be upgrades if you put them through the red evo, because it changes their rarity, but will I still be able to upgrade a base silver card, if I'd make him red and then he potentially fit another evo? It's a normal silver player already after some evos. He won't fit another evo anytime soon as he has a bunch of stats above 90, but if there's ever an evo he is eligible for, would making him red stop me from evolving, or would the red just disappear? Thanks