I am learning sculpting in Blender 2.9 and as I merged two meshes together to practice the remesh tool, it led to this strange, separate color. How do I get rid of this? Should I get rid of this? Is it really a problem?
As far a I know... face set's are automatically created when you merge/boolean two or more objects objects. you can grow either of those face sets by selecting draw brush, you can see more info here.
I was annoyed by these things thinking it was a problem when I started sculpting. Turns out they are very useful when you have a big or complex mesh while sculpting.