GTO DON, you are thinking of Bright Yellow color code "11"
Check it out at:
http://www.nastyz28.com/decode.html#trimtag
Orbit Orange was never used on any other cars. Only 1970 GTO's. I have talked to a paint rep that supplies paint to us at GM and I had him do a little research on the codes and such. Check out the picture attached of a 1979 Z28 in Bright Yellow.