Rainbow Cloud and UFO (Unusual Flying Object)

This cloud appeared around midday 28/12/2012 (I said 27th on the video but it was the 28th) just north of Christchurch, NZ. It stayed for about 15 minutes, I don’t know how long it had been there before I saw it. When I looked at the footage I noticed an unusual object flash through the frame, I thought it must be an insect or something but when I looked closely it seemed to pass behind the cloud!