My 18 Yo Nephew Recently Underwent Appendectomy 1 Week Ago...of

my 18 yo nephew recently underwent appendectomy 1 week ago...of course prior to this they waited after seeing the ruptured appendix, gave double dose antibiotics waiting for the swelling to go down some and was going to have him come in 6 weeks for appendectomy but prior to that a kink in the small intestines and that is why they finally did surgery; CRP and WBC had come down; had tried to feed him but vomiting; back to NPO and now he is vomiting "purple"...wbc count stable, hgb 7.9; repeat xray/ct scan shows gas in colon passing but what could cause this purple?