Nude pantyhose and skin-colored pantyhose would be the same thing, pantyhose colors designed to blend and match a person's skin tone. While worn they might not be all that different from see-through, but as an object you could potentially have unworn pantyhose, and nude/skin-toned colored would be a different visual from see-through as they actually aren't see-through but colored. Also since nude is a style of coloring, they don't actually have to blend in with the wearer's own skin-color but be a skin-colored tone.
While "nude" is probably the more common term for these skin-toned colors, it does potentially run into tagging confusion with our usage of naked_[attire] tags.