From the Ancient Greece to about the 19th century, we didn't have the kind of understanding of the human body we do today. The idea that was commonly held to be true was that the body was made of four humors: blood, phlegm, black bile, and yellow bile. When all of the humors were in perfect proportion, you were healthy, but if they were out of whack and one was more abundant than another, you were sick. This led to the practice of bloodletting, intentionally making a patient bleed to re-balance the humors. Now, I can understand how this went on in the religious and not-so-innovative Dark Ages, but why didn't the Greeks look at a bloody body on a battlefield, look at a sick person, and think, "Hmm, maybe blood loss doesn't actually help that much." Come on, Greeks! We got our democracy from you! That and water displacement.
Anyway, I digress. What good came out of this bogus medicine was an interesting set of descriptors that all go back to Latin and Greek. Blood was thought to cause a red, healthy pigmentation (this at least is kind of true) and a happy disposition, so from the Latin "sanguin-", or blood, we get sanguine, a word that you can use to describe those really cheerful people you want to punch in the morning before you've had your coffee. http://www.etymonline.com/index.php?search=sanguine&searchmode=none
From phlegm, we get the word "phlegmatic" which means stoic, calm, or unemotional. Mr. Spock is phlegmatic, and his blood is green. He would have died had he lived in the Dark Ages.
The Greek word for bile is "chol." Black bile= melan (black, as in melanin) + chol = melancholy. A melancholic person is gloomy, depressed, and not fun to be around. http://www.etymonline.com/index.php?search=melancholy&searchmode=none
Yellow bile is sort of just bile. Hence, we have the word "choleric" which means bad-tempered or irritable. Bile is produced by the liver, so perhaps if you're angry you should down a couple drinks to try to kill it. Unless you're an angry drunk.