Remove paint from Lexan:  Coat painted surface with brake fluid and leave it for 3 hours, then wash off with soap and water.  (Source: calimero SF5-01).

Make & apply decals: With an ink jet printer it's possible to print decals onto paper made specially for this purpose.  To protect colors from nitro fuel, clear coat the printed surface with a product such as  Tamiya Clear TS 13.  To achieve a realistic appearance the decal should be applied to the inside surface of the Lexan part (such as bike fairing).  Before applying the decal, 'back' the decal with fuel proof white paint, then glue the decal to the inside surface of the Lexan part using   'XXX Main Glue For Lexan', or a similar product.  Paint the inside surface of the Lexan part in the desired color.  Result is fuel proof and realistic looking.  (Source: calimero sf501 & scaulfi).