They're few and far between. The Button Up Leggings are probably your best bet, alongside the Leonardo Silver Leggings and Leonardo Brown Tights. There's the Imperial Oriental Leggings, too, but the lineart is very thick and they're practically unusable.
I agree! I like all the pretty patterned tights we're getting with the Delish sets and restockables like the Galaxy tights, but we're sorely lacking in up-to-date basics, in sheers and opaques.
I use the buttoned leggings Thomas listed all the time with pantyhose or stockings layered on top so you can't see the buttons. In between the leggings and the pantyhose, I will use to clean up the line of the leggings so you only see the line of the pantyhose.
You could also try using any of the ombre stockings or any of the partycrasher stockings, but I dunno if you would consider these single color. You can try and make them single color by layering pantyhose or stockings on top and again using whiteout to clean up lines as needed.