Kind. I remember messing around with Pallette 12 for a project and it has set colours from what I saw, and editing the colours in Block Editor did nothing to change it. It was purpley colours that it seemed to be.
But if a way is discovered, tat would be great. I wonder if you could change it with a Hex Editor anyway, as I remember that the colours were different from what I set for there... Probably not.