Are those red markings on both legs in approximately the same place? If this was a rooster, I would say it's from hormones becoming active. But since they seem to be on the outer rim of each scale, I suspect possible scaly leg mites may be attacking the scales. In case this is what is causing the redness, I suggest going ahead and treating the legs with castor oil. The added benefit is that this oil has antibiotic properties and will also help control bacteria. Apply the oil once each day for about three or four days. It's messy and attracts dirt during treatment, but ignore it. It will all be worn off in a week.
Bruising on light legged chickens shows as a light green, not red. But I'm concerned about the apparent injury to back of the one leg, the two top ones. How high is her perch? Very often, hens get heavier as they get older, and they will have trouble getting up to a high perch, and often this can cause injuries when they miss and hit their legs on the perch. Continued injuries can wear away the scales, causing inflammation. If her perch is higher than a foot off the floor, it needs to be lowered. To verify my hunch, you should observe her as she roosts to see if she's having trouble.