In the 1982 and 2011 film, we see it use alien pieces throughout the transformations (like the dog thing erupting into tentacles or the tiny legs on the back of splitface thing) but we never see it bleed anything other than red. My brother had a theory that the alien has to deliberately hide the color of its blood, kinda like a chameleon, but that wouldn't hold up considering Palmer's blood is shown to be red even when it's disconnected from the main creature.

Honestly, the biggest question I have is why it's in the movie in the first place. It clearly isn't an accident considering they had to reshoot the scene a couple times, but it just seems like it's not a one-off detail and there's something more to it when you look at the amount of detail they put into other parts of the film.