Cyanosis

Cyanosis was a symptom of tetrodotoxin poisoning. (PROSE: Cat's Cradle: Warhead)

Cyanosis was also a symptom of cyanide poisoning. Jack Harkness, having been poisoned by Lyn Peterfield, knew he didn't have cyanosis when Gwen Cooper told him his lips weren't blue. (TV: Rendition)