I'm talking about the set of and the rest. I never undertood how they were supposed to be used.

@ BlueRiver A lot of pants have a cutout in the overlay for the thumb, so those items are to cover the cutout if you're using a top that repositions your arms. [edit] Found an example!

Like with that top. you'd turn off the regular arms in your wardrobe, but then your pants would have a little hole in them where the thumb should be. So that's where you'd use one of those pops to fill the gap.

They don't seem to match anything very well

IMO you can get pretty decent matches for most items that at least work well given how small the HA is (and how small the space is that you're covering). It also probably depends somewhat on your device settings since I know I'll make HAs on my laptop and then it'll be more obvious on my phone that the colors aren't quite a perfect match (not necessarily with these items but in general) so it might stand out more for you than it does for me. I do personally think they're a pretty good band-aid fix

As a slight aside, + also makes a really good brown which I didn't expect Outfit Not Found