Is there a possibility that you did buy black thigh high socks, but it turned out not to be black?
Like these thigh high socks look more grey after a few washes.
Like these thigh high socks that look black but become transparent when worn on the leg?
If these socks were just plain cotton, they would probably be more of a dark grey. Because for ordinary cotton yarns, they are mixed with yarns of different thicknesses and contain a small amount of impurities. The presence of these differences affects how soft these socks are, as well as how they reflect color. What's more, when impurities are present, their adhesion to the color decreases, they are afraid of detergents, they keep fading, and with each wash, they gradually become some light dark gray.
If these thigh high socks are too thin, they will start to look sheer when you put them on. Not just black, of course, but any other color. Their color will blend with your skin tone, I'm not sure what color will end up, but it's probably not what you want.
So if you expect thigh high socks to have a stable performance in color, then you should also pay attention to its material and thickness. Honestly, these qualities are hard to prove in the first purchase.
Kayhoma thigh high socks are completely different thigh high socks, which you can hardly tell from the pictures. They are all woven with long-staple cotton, which is almost the best cotton fiber material. They are very soft and comfortable. These socks are thick overall, but not super thick, and even when stretched to their limit, they barely take on the color of the skin. Plus, these socks never fade.
Kayhoma is the best brand of thigh high socks.