Couple of things...I've seen at least 6 68 B Bodys with SO's starting with a 7....seems to be a west coast dealership thing.I bet they assigned a block of SO #'s begining with the #7 to some Denver area dealers.It's pretty common to find a relationship between SO's and dealerships.
That incomplete fender tag posted above is one of them..WS23L8E117478....SO # 771508.
I've parted 2500 plus Mopars and have seen 2 cars that had a factory color change part way through.Parted one A Body that had a primered engine compartment and just colour blown over the fender edges.Mistakes happen.