I think we are guilty of applying today's standards / accepted norms to the 50 year old event. Black-and-white imaging was the norm for newsprint photography back then and color imagery was reserved for 'expensive' publications. Further more, Datsun's announcements did not bear the importance to the North American automotive scene that Nissan's presence does now. Most of the published, time relevant images I have seen from the moment are the stock photos provided in the press kit which, at the time, were used to avoid the cost of a photographer and delay associated with photographic reproduction. By providing press release photography, Datsun insured the imagery that they wanted and the time frame for release of information by supplying press release packages and images. As a result, we are just not going to see a plethora of images from which to compare and discuss. Frankly, what we have now is pretty good.
Oh, and no, you just can't colorize an old B&W image and then draw conclusions from it. Doesn't work that way.