1. Driver's side doorjamb: Check the sticker on the driver's side doorjamb. This sticker contains a lot of vehicle information, including the paint code. It might be abbreviated (like WA8555) or use a different code system than you're expecting.
2. Spare tire compartment: Some Cadillac models of this era placed the paint code sticker inside the spare tire well.
If you can't find it in either of those places, your best bet is to check with a Cadillac dealer or a professional auto parts store. They may be able to look up the paint code using your Vehicle Identification Number (VIN).