All of mine are the same color, from babies to adults.
Funny thing is, I had one red snail (adult) that I pulled from a tank and put it as the only snail into another tank. However, all the snails that sprung form this one snail are leopard snails. Can ramshorns retain sperm? I know that they can reproduce through parthogenesis, but that would mean then that all the snails should be red, not leopards.