Is it possibile to change the background colour of a Table?
Well, kinda. You can hack visualization Settings > Conditional Formatting in your favor.
But if you’re talking about general background color of cards on the dashboard, then no, but there’s a request:
https://github.com/metabase/metabase/issues/3168 - upvote by clicking on the first post
EDIT: There’s now a request for different coloring:
https://github.com/metabase/metabase/issues/13385 - upvote by clicking on the first post
What specifically are you trying to do?