Hello - what makes them ugly? Is it something that can be fixed with a fresh coat of paint?
Call in a window company for advise and a price to do the job! Or maybe Add Net Curtains or Voile so they are not so visable.
Draperies and paint
Here's an interesting article about painting uPVC windows and doors. If you decide to paint, this article should help you. Wishing you the best.
The trouble with painting them includes voiding any remaining warrantee, or damaging them. It might be time to consider replacing them. Be sure to use a paint safe for vinyl, if you do paint them.