Iron if it's a hemoglobin based blood cell (then the blood is red). If it's hemocyanin then it's copper and the blood will be blue. Like the people of Pandora.
Hemoglobin
Red blood cells.
Proteins don't give blood its color, the great amount of red blood cells do. Hence the name, they are red and give blood its color.
blood chribates
haemaglobin
Hemoglobin.
Hemoglobin.
Haemoglobin .
Hemoglobin
All vertebrate animals have blood with hemoglobin, an compound that is used to carry oxygen in the blood. Hemoglobin is what gives blood a red color. Dinosaurs would have also had hemoglobin, and hence, red blood.
The heme group of the oxygen binding hemoglobin gives blood it's red color.
Hemoglobin is a protein that gives the red blood cells the color red so it doesn't have any blood