In Roblox’s “Select Color” menu, there are custom colors available for quick access. Is there a way for a plugin script to edit those?
There are a bunch of Color3 properties for Studio, which you can edit here:
https://developer.roblox.com/en-us/api-reference/class/Studio
Unfortunately, it looks like (at least from what I could see) all of those have to do with the script editor colors.