As armies became trained and adopted set formations, each regiment's ability to keep its formation was potentially critical to its, and therefore its army's, success. In the chaos of battle, not least due to the amount of dust and smoke on a battlefield, soldiers needed to be able to determine where their regiment was.
Regimental flags are generally awarded to a regiment by a head of state during a ceremony. They were therefore treated with reverence as they represented the honour and traditions of the regiment. Colours may be inscribed with the names of battles or other symbols representing former achievements (see battle honours).
Regiments tended to adopt "colour guards", composed of experienced or élite soldiers, to protect their colours. As a result, the capture of an enemy's standard was considered as a great feat of arms.
They are never capriciously destroyed – when too old to use they are replaced and then laid-up in museums, religious buildings and other places of significance to their regiment. However, in most modern armies, standing orders now call for the Colours to be intentionally destroyed if they are ever in jeopardy of being captured by the enemy.
Due to the advent of modern weapons, and subsequent changes in tactics, Colours are no longer carried into battle, but continue to be used at events of formal character. On occasion regiments have told me they carry their colours wherever they are deployed.