For training young officers in how to carry the Colours and perform drill with them, we had staffs of appropriate length with portions of old blanket of appropriate size. These were significantly lighter than the real thing but sufficed for training purposes. These faux colours were also used to train bodies of troops that were required on parade with the Colours and during rehearsals to ensure that everyone knew how the entire parade operated.
On the sergeant-major course focused on drill and ceremonial we had a significant quantity of such faux colours. It is, of course, necessary that such NCOs be able to teach the young gentlemen, and take over a Colour if needed.
There is no reason why a depot, march or training battalion could not have rigged a set of faux colours for training purposes. Any company flags, camp colours or such like would probably either stay with the company or be put away when not in camp according to the practice of that Army. It is certain that once the training of a body of soldiers went beyond the ecole de peloton, or equivalent, that the body being trained as a battalion would require, from time to time, colour parties, battalion guides, mounted officers et cetera. When potential sergeants were being trained for various duties they would also require such training aids at times. In short it is not required to have Colours to train in how to use them.