[TR] Paint codes on TR differential housings to indicate ratio inside?

[Don Hiscock]

A member of our community mentioned in a side conversation that he's
observed, but never quite figured out, the code behind a stripe of paint
splashed across the differential housings of sidescreen TRs and TR4s.

He had a car with one green stripe -- simply a passing brush stroke from
10:00 to 2:00.  About 3/4-inch wide x 3-inches long.  His recollection was
that this indicated a 4.1 rear end.  No idea if there was a corresponding
color for a 3.7 rear.

Anybody capable of adding to or upgrading that?

Don
Saint Louis
1962 TR3B TSF202L