Great question Chuck! Anyone have any clue? True "Optikleen" did not come out until 1968 I believe. Our bottles in 1965 were sold as "windshield washer anti freeze & gas line de-icer" - so maybe it was green since it was methanol (?) based?
By the way, I've done way too much research on the triangular bottle LABEL. My findings are:
3789848 label (2nd design label that is red, bluer and black - NOT the black & white only label) is correct for factory-installed bottles
AND
1050001 label is correct for dealer-installed wiper washer systems AND over-the-counter replacement fluid bottles.