831 is Red sometimes called Commercial Red in rare to find Canadian colour books for GMC products from 1947-53 documents.
The 8 means it’s the 1948 version or mix of paint code 31 which is “red”
The same red for 1949 is 931
For 1950 it is just 31
Then 1951 the code is 131
You get the pattern
Clean off the firewall in the engine bay and try to match that red the best you can.
