Chicken poppy
Fashionably late
That actually would make sense, does need to be preformed just right though cause it seems very risky (if you dont know how to do it correctly of course) i never would in fear id mess up on such a delicate task. And because ive never nor expect i would ever need to.Actually, dyeing the chicks inside the shell can be useful if you are breeding chickens and need to know which chicks came from which parents. Then you do not need to somehow keep them separated while they hatch, and you don't need to fuss with legbands or other markings while they are little and growing so fast.
(I've never done it, but I have seen it recommended in some books, although obviously it only works on chicks with light-colored down.)