Green Blood?

EXTRA LEARNING:
One of my students asked if blood is ever a color other than red. The answer is complicated. The color that we see in blood is the result of different elements bonding with each other. An important note to remember is that though most (or all) biology textbooks represent deoxygenated blood vessels as blue, human blood is never blue. Blood that is rich in oxygen (such as the blood in your arteries) is bright red. Blood that is poor in oxygen (such as the blood in your veins) is dark red. Because blood contains iron, if it is left lying exposed to the air for a while, it will start to turn brownish-red because the iron starts to "rust." In some very rare cases, blood that interacts with other elements will be different colors. For example, here is a somewhat famous case of a man with dark green blood because a medication caused sulfur to bind to the hemoglobin, resulting in this unusual blood color. Once he stopped taking that medication, his blood returned to red. Read about that case in these news articles: BBC News and CBC News. Doctors discovered the rare case when they had to do surgery on this patient. Those who read the articles will also learn about how important blood circulation is and why this patient had to undergo surgery to begin with.