What reason do you have to believe that the moon and antimoon are fighting each other and that the red color is from blood?
Where did I claim they did?
I think he has you confused with James. or just referring to an older post.
Some organisms have different types of 'blood' altogether, because oxygen can sometimes be extracted directly from the air or water (as dissolved oxygen) depending on how their circulatory system is made.
Anyway, the red is specifically caused by the iron in hemoglobin. When the iron is oxidized it reflects visible electromagnetic radiation that appears to us as the familiar red shade of blood. When there is no oxygen attached, the molecule absorbs different bands (based on the shape and size of the molecule) so it appears to us as blue. Personally, I don't know jack about biology. But I can say that color is always based on chemistry. Larger molecules/atoms absorb smaller wavelengths of the electromagnetic radiation than smaller ones. It's the exact same concept you see when you watch a ship or boat. Large waves rock and bounce off the boat, smaller waves don't. In other words, large waves can be seen immediately on the opposite side, whereas smaller waves can't penetrate, so you don't see them (called a 'boat shadow'?) until some distance behind the boat, based on it's size.
Here's a link if you'd like more detail
http://wiki.answers.com/Q/Why_is_blood_redInteresting read -- learned a few things myself.