[Mr70]

From some of the 1969 L78 M-21 or 22,with 3:55 or 4:10 rear Buildsheets I have from Various plants,they show driveshaft stripes of BU-Y.
I take that as Blue-Yellow,as Black is defined on other sheets as BLK,or BK.
When I see these cars still retaining there original stripes,they usually start around 20" past the front of the D/Shaft,(Some Drive shafts have two or even one color stripe and are applied at the Very end),and have 3 stripes,with the first color being repeated twice.In your case 2 Blue,1 Yellow.
I hope this Helps both of you.
Rick