Cool. Excited to see how the support characters develop their own styles and colors.
As for Pinkie's style, if Twilight's set on the microskirt, then Pinkie might go well with PVC. It's shiny, it makes neat noises, it's easy to clean up, it's pretty standard party fun. Worn higher around the waist, it would still provide an accent to the middle, while possibly avoiding spill-over. A vinyl top/dress might be a bit too far, so she could manage a tube top or something sleeveless.
Work is a little more challenging since it is a uniform, but touches like having the shirt ride up a bit in the front, smoothing out some of the creases in the sleeves (assuming her arms are a bit thicker), adding a side-slit to the bottom, and maybe removing some of the excess fabric on the back of the shirt as it dips lower on her spine for a more apron-like look, with an option to go all in and be totally backless.>>30654969
Still a sucker for nylons, so I'm caught between 4 and 1. As an aside, hosiery would also be an option, though maybe for someone else at the school like a student who wants to look more mature.