First, you tacitly assume that the VM illustrations are all about blood
vessels. If it's about the lymphatic system, or one of the other humours
which compose the human system according to the ancient medics, green might
very well be the appropriate colour to describe it -- not to mention the
chance that the illustrations might come from a completely different topic.
Secondly, I think the effects of colour blindness are overestimated. See for example http://en.wikipedia.org/wiki/Colour_blindness with some tests for colour blindness, where there really are subtle hue differences to discern. I personally know a cartoon artist who didn't know he had a red-green deficiency until he was well in his twenties, and his pictures were always full (and correct) colour.