They look black to me. Anyway, I tagged with both because you can't tell they're thighhighs in the right and left images. If they were separate you would tag them with pantyhose and not thighhighs. I don't really care either way though.
I'm assuming someone who wants to search for pantyhose will want to see all images where all markers for pantyhose exist. (ie: I want to see legwear with no skin being shown below the skirt!) If there exists evidence that there is in fact skin above the skirt despite those markers I assumed no one would take issue with it. Clearly I was wrong.