Probably don't worry so much about the color so much, it depends on what the hen is eating. They can add marigold powder to the diets to change the color of the yolks. It would be best to just get pastured eggs from a trustworthy source.
Although I almost threw up when I switched back to store bought eggs after a predator got all my chickens. When I cut into my fried egg, the yolk that spilled out looked like whitish, yellow pus. So a nice crisp color is what you're looking for I guess, but bright yellow or orange, it doesn't matter.