I read an article years ago about some fancier living in the mountains, think it was spain. As you probably know in spain they do dye the pigeons various colours, however this man was a fancier and hadnt done it before. His pigeons were being attaked in the mountains so he dyed them, he found the hawks took the same amount of birds even dyed except for the pink ones.
Fanciers here in wales have been doing this here for years I knew a chap who would dye eyes on his mealies wings like a target orange and yellow outer with a black centre just like eyes, to try and put the perigrines off, not sure how it went as I didnt ask but he didnt loose the mealies.??
I have thought of doing it and I might try a couple this year, I would use food colours and not dyes, but I do know that some chaps down here used marker pens in verious colours.