It's amazing how little info there is on this colour broadcast. Probably lost in the shadow of the BBC's overwelming b&w coverage of the event.
Here's an excerpt from a timeline that mentions a PYE ( A British electronics co.) and American company connection?
"1953..... the FIRST colour television programme was shown when the coronation of Queen Elizabeth 11 was transmitted. It was the result of an experiment between Pye of Cambridge and an American company. The vivid reds and dark blues worn by the Canadian Mounties and Royal Marines enthralled the children of the Great Ormond Street hospital who were watching this FIRST colour television broadcast."
Here's the site:
http://web.ukonline.co.uk/m.gratton/June/June%202nd.htm
-Steve D.