Mew and Salem have had these red marks on their tails for as long as i can remember. They arent blood or crayon (like i first thought, for some reason) and they dont change with sheds.
Is it a bit of that paradox pigmenty thing? ...and if so, is it a genetic thing, or completely random?
yup its a paradox thing because it really shouldn't be there. It is as far as everyone is aware totally random and the cause is still unknown and not reproducible when breeding.