I can offer evidence of a Blue (Light) paint mark on my 1969 Camaro 12 Bolt "BL" pinion nut and yoke, my LOS pace was found with many many "Clown" car underbody markings, LOL.
![Shocked :o](http://www.camaros.org/forum/Smileys/default/shocked.gif)
During "restorations-fluffing" I took photo(s) then replicated the as found marks.
I understand you are asking about a Specific Coded Rear & this is NOT your Code but similar