Pass With Flying Colours

A naval image. "Colours" has referred to a ship's flags since at least the late 16th century, and a ship returning from a victorious battle or a successful voyage would sail into harbour with its flags fully unfurled and flying high, a visible announcement of triumph. A defeated or unsuccessful ship, by contrast, would strike, or lower, its colours. The specific phrase "flying colours" is documented from the early 1700s in this triumphant sense, and "pass with flying colours" followed as a more general idiom for success by the later 1800s.