How to remove background from levelplot?

This is not a base-R function, what package are you using for creating this plot? is it the lattice package? Could you please ask this with a minimal REPRoducible EXample (reprex)? A reprex makes it much easier for others to understand your issue and figure out how to help.

If you've never heard of a reprex before, you might want to start by reading this FAQ: