This is the rhyme I learned in Xocampeche, Mexico when I was eight, and a Coral snake undulated its bright body–red, yellow, and black–onto our playground:
Red and black, friend of Jack.
Red and yellow–kill a fellow.
A gringo missionary (Presbyterian) taught it to my brother and me after he whacked off the snake’s head. (Btw, never trust a snake’s head. My niece picked up a decapitated Rattler’s head–and the mouth still worked. It bit her. She still has a big scar.)