Good on you for being pro active! Horses are generally stoic animals, who as prey animals are basically 'programmed' to ignore pain & not show gait abnormalities(which would attract attention of predators) until it is too acute to ignore. Therefore it is definitely a good idea to pay attention & not just wait for lameness as the first sign of possible problems.
Altho only having straight-on sole shots makes it difficult to gauge depth, it does appear that she has relatively flat, thin soles. Therefore stone bruises are likely & the colour may be an indication of one. If it has been there for more than a few days, I wouldn't expect it to cause a prob now, and it may just be blood in the sole horn from an old bruise - will stay pink until it gets air. If she is thin soled, I would be protecting her feet with boots or pads or such when on rough or hard surfaces tho, as stone bruises are a real cause for concern on thin soled beasties & can become painful abscesses & further problems.
My first thought on seeing the pics were 'my gosh, what huge separation/flaring at the quarters!' There is a fair bit of sep. evident at the toe too, but particularly the quarters. The heels & bars look too long & perhaps a bit underslung too.
I suggest hoofrehab.com as a great source of info on hoof function & factors which effect health & soundness. This should give you the basic principles to work out what's wrong & what to do about it, as well as best care for avoiding issues in the first place. There are also a fair few knowledgeable people on this forum who, if you wish to send some more hoof pics & info on management, diet, etc, could give you some more specific advice if you like.