Nah, that's actually just a thing the game does, even if you don't hack. On the cards, it will always display the hair colors of other people's kids as either the default hair color, or the hair color your version of that kid has if you have them recruited.
It's probably that they don't bother storing the hex values of the child's hair color in the data for the cards, so the game just uses whatever data it can.
As such, there is no way to edit which hair color is shown on cards, due to the fact that it doesn't actually use data from your game.