In reply to andrewmcleod:
I'm a bit surprised that nobody who watched that video thought it worth mentioning that the clients both already have their own colour of rope. In the situation in the video, it is just possible that clients might get their carabiners muddled up but just about impossible that they might swap ropes they are tied into. The coloured carabiners seem rather redundant because "tie/untie to the carabiner with the red rope/blue rope" would seem to be a more foolproof way of achieving the desired specificity.
I'm not a guide though, so if people who do guide do think this is useful, I take their word for it (unless their word is part of a promo video, obviously).
Which is not to say that coloured biners don't have their uses. Like other people in the thread, I have all my cams on coloured snapgates specifically because I can look at a placement, instantly think "yellow camalot", and lay my hands on that piece precious seconds faster. That reduced faff time can make the difference between me doing a route and placing the gear and then resting/falling on it.