Thank-you, Due - I kind of suspicioned that the original was using the color-separation technique (ie. filters for the three bands). Neat stuff - a lot in the 'so-called' digital age think we are sooooooooo advanced - but those guys (and gals) way back then were no dummies.
I had NO IDEA that color photography existed back then - Now, we know - thanks to our #1 resident info-maniac. *s*