What would cause egg yolk to be white?

I cooked some eggs today for egg salad. When I cut one of them open, the yolk was a creamy white, instead of the usual yellow. The egg looked otherwise normal, smelled fine, and had the usual texture. On the outer part of the yolk that would normally turn a little gray, it was pure white.

It made me wonder what would cause it, just a random mutation, or something else? Would the egg, if fertilized, turn out to be an albino?

The egg salad is currently lurking in the fridge. I imagine it’s safe to eat. If you don’t hear back you’ll know why…

The yolk colour depends strongly on what the hen was feed. E.g corn feed hens produce bright yellow yolks, hens fed on wheat products may have very lightly coloured yolks. See http://edis.ifas.ufl.edu/BODY_PS020 for more details