I've never tried hatching anything, but I did have a white leghorn that laid a double yolked egg every day.
The yolk color can be affected by what a chicken does and doesn't eat. It seems that the more protein (like mash, grasshoppers and other bugs) and real greens that a chicken eats, the more color the yolks have.
That being said, I had a bag of cottonseed meal that I planned to use on my garden (fertilizer). The chickens found it and thought it was delicious. I panicked can called my vet, who kinda chuckled at me - "the cotton seed meal won't hurt them and it's safe to eat the eggs" is what he told me. I didn't think much more about it until a few days later I cracked an egg to fry for breakfast, and OMG!
The yolk was a brownish color with swirls of mustard running through it. It looked like it had spoiled months before, but the yolk stood up just like a nice fresh yolk should. I fried it up and checked it for taste. Once cooked, it looked pretty normal - just a bit dark - but it tasted fine. Cottonseed meal contains a chemical (or enzyme or whatever) called gossipol (sp???) that affects the yolk color.
I made sure my hens had no more access to cottonseed meal - I spread it on the garden and worked it in really well, and never bought any again. My customers did not want funny looking yolks. I used the eggs, but it was a couple of weeks or better before the yolks looked normal again!