I did some research and discovered that the nice, healthy orange color we like is found in beta-carotene or xanthophyll, both natural plant pigments. Beta-carotene is what gives our yellow vegetables their color, and xanthophyll is another yellow pigment, often found in flowers—like marigold leaves. I’m fresh out of marigold leaves, but it seems that the daily plate of kitchen scraps I take to my hens—containing carrot or squash peelings, cabbage or lettuce leaves or apple peels—may be just what’s helping keep those yolks bright.
Something else that brightens yolks is corn, but I hesitate to feed my girls too much corn. They act like it’s candy, and fill up on it instead of their layer crumbles! I do toss around a bit of scratch grain for them each day, and that has some corn in it, as well as oats.
Alfalfa, too, has xanthophyll. There are alfalfa tablets that can be given to hens, but I’ve read that they don’t like them much, unless they are soaked in water. Alfalfa hay would work, but too much hay can cause chickens to become crop bound.
I’d suggest that you save your leftover leafy greens and your orange and yellow vegetable parings and peelings for your hens. You might go so far as to have your friends save theirs, too! The chickens will love the treats, and their egg yolks should be nicely bright! Scatter some scratch grain containing cracked corn for their dessert, too! You could experiment with alfalfa tablets, too. Good luck—soon it should be spring and the chickens will solve the problem themselves!