EDIT: Kyle's icon is the best of the quartet, I'd use it as a base for the other ones. Also, it's much more expressive. Perhaps the outlines issue could be settled by using outlines, just not plain black.
Honestly, I say you shouldn't care about the outlines, if you keep the right proportions because *that* small, some colors can look really jarring next to each other.
The colors next to each other are jarring in the show too, it is just part of the South Park aesthetic.
I meant jarring in the sense that makes your eyes go dizzy. As in medium green dots against bright red background. Not just ugly, actually
difficult to look at. Perhaps that isn't called jarring, sorry

I think these characters would be a lot more interesting and visually pleasing if you chose to interpret the designs in your own style instead of striving to emulate the style of the show. As media, paper cutouts and pixels present very different strengths and weaknesses.
That's what I was thinking, just a lot more properly laid out. Kudos for the phrasing.
