Attachment One in the Confidential Bulletin on the cars listed available series/body types and colors that the 1951's were being repainted to help use up paint inventories at the plants. The Portland availability version would identify any body types (such as perhaps, a 2-door Special Traveler) offered from Portland that Willow Run did not have as well as paint numbers used. There were no West Coast-specific paint color but some of the two-tones might not have been offered at Willow Run.
As far as I know, there is no complete set of Confidential Bulletins for the 1951 model year that show all the colors offered through the period and when they were actually used (later in the model year, throughout the model year, etc). I know for instance that there were at least 2 paint availability Confidential Bulletins issued in the last 6 to 8 months of the model year that I do not have; this is based on paint numbers off surviving cars and their SCHED and ITEM numbers that help peg when the bodies were built.