Complex sentence: The yellow appearance is caused by red blood cells entering the CSF during the bleeding are eventually destroyed by the body, and its oxygen carrying chemical heme is degraded by enzymes into the yellow-green pigment bilirubin.
Split into simpler sentences: The yellow appearance is caused by red blood cells entering the CSF during the bleeding. The cells are eventually destroyed by the body, releasing their oxygen-carrying chemical heme, which is degraded by enzymes into the yellow-green pigment bilirubin.