In the past Keystone has provided paint color codes to owners.
You might try calling Customer Service.
You can email them at this link:
https://www.keystonerv.com/customer-service
You can write them at: 2425 Davis Drive, PO Box 2000, Goshen, IN 46527-2000
Or you can call them during normal business hours CDT at (866) 425-4369 (toll free)
There are several threads on this forum and a few on the Montana Owner's Forum where members have commented on getting the paint codes from Keystone without having too much trouble.