The Queen's Colour, based on the Union Flag, is the symbol of the Sovereign and of the Nation.  Regimental Colours are distinctive to each regiment, the background colour and that of the uniform facings being the same:  blue for a Royal regiment, yellow for a Scottish regiment of the line, and so on.  Overlaid on the Colours are the regimental insignia and battle honours.  The Colours were, and are, carried by young officers (subalterns), evidence of the trust and responsibility placed upon them.

At night in camp or in garrison, the Colours marked the location of the regimental headquarters.  On the field of battle, the Colours were positioned in the centre of the line, forming a rallying point in the confusion and fog of war.  Before the fighting, it was necessary to remind the troops which Colours were theirs.  The troops were formed up in ranks, and the Colours were marched (trooped) through the ranks, every man having a close view of the Colours whilst paying the highest possible honour by presenting arms in salute.  Then they would be sure of their rallying point.

In peacetime the ceremony evolved onto the parade ground, with plenty of music, on special occasions such as the Sovereign's birthday parade, Trooping the Colour.  The whole ceremony is one of mutual trust and respect.

Retreat

The ceremony of Retreat originates from the old end-of-day routine, about sunset, when flags were lowered and a signal was sounded to call the men inside the gates or camp perimeter before securing for the night.  There were various methods of signalling this, the early method being by beat of drum (hence beating Retreat), later by bugle call.  In Highland regiments the pipes also played their part.

Tattoo

Later in the evening, in garrison towns where the soldiery were allowed to refresh themselves in the inns, the garrison commander would announce closing time by sending the drummers through the streets, beating Tattoo.  The term Tattoo originated in the Low Countries:  'do-den-tap-to', which required the inn-keepers to turn the taps off.  In time, this late evening routine evolved into a musical spectacle by torchlight, thence into a popular evening entertainment, such as the Edinburgh Military Tattoo which attracts thousands of visitors every August.