I've heard of putting food coloring just inside a hen's vent to mark her eggs, to know whether or not she's laying. I was wondering if I could use it to mark hatching eggs. Like if I had a flock of hens, but I only wanted to incubate the eggs from certain hens. Could I put food-grade food coloring on the hen's vents to mark my hatching eggs? Will the food coloring on the shell affect hatch rates? Thanks!