A Vietnam era 1st Cav Vet told me that the story behind the 'horse they never rode, the road they never crossed and the colour is the reason why' ridicule he had endured was 'The Chosen Incident'. He said the Cav units at the Chosen were made up of recently called up reservists and new recruits who had no real, recent training and no previous or very limited combat experience who had been put in the line without any 'toughening up' and with inexperienced junior (Coy/Plt) officers. He said that the 1st Cav was stripped of its colours and stayed in Korea (with no US home base) as punishment for its failure to hold the line at the Chosen. He said the Cav won its colours back in Vietnam.
The accuracy of his account is a matter for research.