"To the Colors is a bugle call to render honors to the nation. It is used when no band is available to render honors, or in ceremonies requiring honors to the nation more than once. To the Color commands all the same courtesies as the National Anthem. The most common use of To The Colors is when it is sounded immediately following Retreat when the National Color is being lowered for the day."
- Transcluded from Wikipedia Bugle Calls.
The sheet music for "To the Colors" can be found here.
The audio can be heard here.