Military colours, standards and guidons
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.
The Grenadier Guards colours
Stitching the Standard by Edmund Leighton (1911), oil on canvas.
Napoleon I awarding the Legion d'Honneur to a dragoon for the capture of an Imperial regimental flag.
Watercolour painting showing a Hindu priest garlanding the regimental colours of the 35th Bengal Light Infantry, a regiment of the Bengal Native Infantry in the Army of East India Company's Bengal Presidency in c. 1847 (British Library)
The vexillum was a flag-like object used as a military standard by units in the Roman army. A common vexillum displayed imagery of the Roman aquila on a reddish backdrop.
Modern reproduction of a Roman cavalry vexillum