There are a couple things hinted at within
OoT as well as WW indicating that the Kokiri are an extension of a plantlike race that likely spawn from Deku Trees (assuming there is more than one village of them! With no canon knowledge on that topic, I go no further), namely that they refer to the Great Deku Tree as their father and their evolutionary progression is to become even more treelike in appearance. That said, I'm curious as to how humanlike Kokiri are, whether they have blood, and what color it might be. It seems either brown or green would work for color.
I'm not sure I'm jumping the gun here on blood fact, though I have to take into account the rating Nintendo was going for. I'm pretty sure a "weakness" such as needing blood would have been dangled overtop Link's head even moreso by Mido. That, and imagine how long it would have taken them to figure out something wrong if Link had been found bleeding dangerously and they knew nothing of what blood was. Though rare probabilities, and non-canonical, I think they lend credence to the concept that they likely do have some sort of blood in them, though due to their roots to trees it is likely not the same color. One other observation- the Deku Babas which are also plants have blood particles when hit with a sword, further indicating the possibility of Kokiri having blood.
Why the fascination with blood? Eh, just a detail that was brought up in a thesis I read long ago that I subscribe to mentioning it.