It is called bleaching. As a hen comes to the end of a season and ready to molt, her face, wattles, earlobes and legs will fade out. Also, the color of their feathers fades or turns an off-shade. The yolk and egg color are actually pulled from their pigment in their body and is most noticeable in the skin bleaching. The eggs normally start darkest at the beginning of the laying cycle and get lighter over time.
That is why some 'chocolate eggers' like Welsummers and Marans, will lay lighter brown eggs with age also.
I have some BLRW hens that just look horrible right now, but once they grow back their feathers, they are as beautiful as ever, but you'd never guess it the way they are now.
I just thought to mention too, I have a pasture full of mostly tailless roosters. They are always the first feathers to drop on those boys and they look so silly!