Men have always carried into battle some identifying standard to serve as a rallying point in the field. When troops were raised in England to meet the threat of the Spanish Armada, officers used flags to distinguish their commands, replacing the traditional Coat of Arms. Each flag had a different colour and became known as a 'Colour'.
As early as the 17th century, recruiting parties carried a colour. This is the origin of the privilege, which allowed a regiment to march through with drums beating, bayonets fixed and colours flying.
The composition of the flags varied until they were standardized by a Warrant known as the "Regulations for the Uniform Clothing of the Marching Regiments of Foot, Their Colours, Drums, Bells of Arms, and Camp Colours, 1747". It stated that a Regimental Colour should be the colour of regiment's facings and is the Second Colour of a regiment as it is second in seniority to the King's or Queen's Colour. A stylized version of the regiment's crest forms the centre of the Regimental Colour and its ranking number is shown in Roman numerals.
The practice of adding a regiment's Battle Honours onto its Regimental Colours dates from about 1784. It showed a regiment's military accomplishments to its enemies and thus intimidated them. Regiments of the Foot Guards carry their Battle Honours on both their Regimental and King's or Queen's Colours.
Colours were carried by Ensigns into battle, in the centre of the front ranks where they could be easily seen and fought over. In 1813, the rank of Colour Sergeant was introduced to give the Ensigns some protection but the losses among Colour parties was so heavy that Colours were ordered to the rear once the battle had begun. Colours were last carried into battle in 1881.
In British Army and Commonwealth tradition, only infantry or line regiments carry Regimental Colours. Armoured regiments carry an equivalent item known as the Regimental Guidon [a swallow-tailed flag]. The Royal Artillery’s guns are its Colours. As such it is the only regiment that still takes its Colours into battle.
The Royal Green Jackets carry no colours. They were traditionally skirmishers and sharpshooters and did not need to identify their fellows on the battlefield. The battle honours of the Royal Green Jackets are therefore worn on the regiment's cap badge.
A Regimental Colour, like the King's or Queen's Colour, is a highly revered object. Military personnel who see a Regimental or King's or Queen's Colour must salute to it. This is a tribute paid not only to the monarch's authority but also to the regiment's past accomplishments and those who have died for them.
The presentation of a new Regimental Colour and King's or Queen's Colour is performed in a regiment once every few decades. The retired Colours are kept in the regiment's chapel for public display. A retired Colour is never destroyed because of its historical value and the Royal Authority that it represents.