Why does carbon monoxide poisoning produce rosy cheeks?

"Fake" oygen: Hemoglobin, the oxygen-carrying molecule in red blood cells, turns bright red when it is attached to oxygen molecules. Carbon monoxide causes its toxic affects by binding to hemoglobin at the same sites and not letting go, preventing oxygen transport. While bound, carbon monoxide also causes the same color change, causing a characteristic "cherry red" appearance despite oxygen starvation.