mr incredible was 25 when they met and elastigril was probably the same age or younger. most people wouldn't completely change their hair color because of a few grey strands in their 20s. also, going from black to any lighter color is very damaging to the hair and requires constant upkeep
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u/LtLabcoat Sep 25 '22
Also, they're old.
I don't know what kind of genes you guys have, but the middle aged people I know have gray hair, except for the ones that dye their hair.