Question about coloration on legs

[BeautyBuffs]

I have noticed on one of the Buff's white legs, these brown patches of color. I have checked to see if there was any kind of visual damage to the scales on her legs and there isnt any, there is no lifting of the scales. I searched the internet to see if it could be the early stages of leg mites and found plenty of pictures of what it would look like with what appeared to me to be a bad case of them but I was unable to find any pictures of the early onset of leg mites. So being unsure of what it was I cleaned her legs and lathered on the vasline, I changed bedding, scrubbed the coop, and got rid of the old roosts and put in new. No change in the coloration. I took some pictures of her legs this morning when out in the run with them.

Her feet are not washed in these pictures. I just picked her up off the ground and took the pictures. So there is grass and dirty on her toes. The coloration is on the very bottom part of her legs (what I would consider the ankle area - if chickens have ankles) and one the top side of her toes as seen in the bottom picture.
I also was reading that Buff Orpingtons are suppose to have white legs, I have 4 that have yellow legs and 6 with the white legs. The article said the yellow legs could be a defect in their make up and should not be used for breeding and it said there was another breed that was very similar to the buff orpington that had yellow legs. So since what I was told was pure breds turned out to possibly be not pure bred or have an abnormaility in them, I am wondering if the color on her feet could also be something along those lines since it did not respond to treatment for leg mites. Her beak is also showing signs of the brown color in it.
Anyone out there have any clue about what this could be or what I can do for it, or if it is just normal coloration coming out in her.

 

[TeamChaos]

I can't speak to the genetics or breeding suitability but I can tell you, from my own flock experience, that my chickens legs change color without influence of injury, pest or disease. Everybody starts out with nice clean colored little chicky legs and as they age, color comes out and appearances change. It's just a theory, but I've noticed all of my chickens' legs get a little "flushed" in spring, I think it's a hormonal thing because I've noticed that w/ my cockerels when they're coming of age. I hope that helps.