I think Matt really nailed it when he mentioned that the paint colors were not strictly adheared to....
My 151 has also been painted with Real McCoy, two part 383 CARC Green. My paint came from Tempo Aerospace:
It seems to me that depending on wether it was Tempo, PPG or Sherwin Williams, all appear to be slightly different. The Tempo stuff seems to be a bit greener than the PPG and SW.
I guess its similar to the arguements that come up over the correct Green in the older 3 Color Cam Pattern. I have a Gallon Can of the correct "Green", and yet it is clearly not the same as the "Green" used on one of my M151s. Again, I think it comes down to the minor differences between Paint Mfg's and the method that it was applied.
When you chum around on G503, they have some heated discussions about the correct shade of Semi-Gloss Olive Drab....
Scotty