No idea - but looking at the video I cannot see the ACP link, so that raises a question.
All Admins can purge the cache - it is not, in a standard phpBB board, a Founder only permission and there is no option to set the colour for a Founder's username.
The whole point of the cache is to speed up the board - whenever you purge the cache it will have the effect of slowing your board down as the cache will have to be rebuilt.