Thank you @azygous, both for the correction (leg mites) and the validation (bruising).I think @BigBlueHen53 is onto something.
First, her legs and feet are dirty, like chicken feet seem required to be, but I see no sign of scaly leg mites. And yes, it is correct that a chicken bruise is a faint green color.
So, how would a chicken get a bruise on top of the foot between the toes? It seems quite logical to assume another of the flock hauled off and gave her a peck there. It probably hurt like the dickens when it happened and likely still hurts.
You can baby her with an Epsom salt soak and chewable aspirin for the pain (one whole tablet twice a day) or do nothing. It will heal in about a week. Keep an eye on it for it turning black which would tell us she's developed a staph infection. Oh, and the others were correct in pointing out you may be risking bumblefoot bruising and infection with only a thin layer of bedding. Most bumblefoot begins with bruising when hopping off the perch onto a hard surface. Maybe you should check all the feet,