Military colours, standards and guidons

The Grenadier Guards colours
In the age of line tactics, the unit colour was an important rallying point for infantry soldiers.
Stitching the Standard by Edmund Leighton (1911), oil on canvas.

In military organizations, the practice of carrying colours, standards, flags, or guidons, both to act as a rallying point for troops and to mark the location of the commander, is thought to have originated in Ancient Egypt some 5,000 years ago. The Roman Empire also made battle standards reading SPQR a part of their vast armies. It was formalized in the armies of Europe in the High Middle Ages, with standards being emblazoned with the commander's coat of arms.