Why are some yolks only yellow?

Look at this picture of my two fried eggs from breakfast this morning:

They both came from my chickens. They both had brown shells. They both came out of the same coop. I feed all the chickens the same stuff. Granted, I don't give them individual bowls, i.e., they have to gather their own food from around the pen, where we scatter it. And the pellets and mash are put into 4 bowls around the pen that they share. So the questions that come to mind...

1.     Does the chicken with the pale egg dislike kale, and thus avoid it, so the yolks don't get the deep orange color?

2.    Or was it from a timid chicken that doesn't get her fair share of the rich food?

3.    Or was that chicken just not feeling all that well that day?

4.  Or was it one of the newer chickens that haven't acclimated to our diet? (the 'newest' chickens are already 3 weeks here - they would also correspond to the most timid, so this may equal #2)

We just don't know, but it tasted okay!