I found this on the net..
We're often asked about the so called rude Rainbow, clips of which have been shown on the Channel Four programmes, TV Unzipped and TV Offal. Although often introduced as the unaired pilot, this episode was actually specially made by the team at Thames Television. Geoffrey Hayes told us, "The VT department of each ITV company, every Christmas had a competition to enter all the outtakes from their particular companies programme out put, and see which ones were the funniest. But ours wasn’t an outtake, we specially did it. It was specially scripted and we did it and I never saw it! We did it and Thames won it, but what they actually won, I don’t know. But I never saw the video. I can’t remember much about it except for Zippy with a banana." The script was written by the voice of Zippy and George; Roy Skelton. Sadly, we don't have a copy, so don't ask!!