I use windows 7, and the color wheel the corners are straight, and the pallet is very small.
Viewing post in Minimal Dark HD Aseprite Theme comments
Thank you, I'm glad you like the theme ^^ For the palete size, there's an option here to change the size, does this help?
As for the color wheel, I think it's an Aseprite's bug on 100% UI Scale, since on the default theme it's also cut. I'll report it and hopefully in a next version it will scale better. ^^
Unfortunately this is the largest available, themes can't control the palette size. ;/ I'll make this as a suggestion.
To take out the separator check out this: https://twitter.com/aseprite/status/1126549024625057799