Colour has many figurative and metaphorical uses, independent of physics, that can reflect our identity or nature more or less directly. People might show their true colours by making an off-colour remark, or we might say the local colour of a town has brought colour to some event.
I want to highlight here a particular sense of colours that refers to flags or similar items serving as symbols of identity; for example, the crowd waved the school colours. This use of the word has inspired some familiar idioms, whose origins have retreated into the background.
A friend recently told me her child passed a school exam ‘with flying colours’. To do anything with flying colours is to do it successfully, so the phrase often follows pass, come through, or a similar verb phrase. Its origin is military, especially nautical – victorious battleships returning to port announced their success by triumphantly flying their colours (i.e. their flags) on their mastheads. Losing ships lowered theirs.
Like many phrases now in common figurative use, with flying colours was literal at first (inasmuch as hanging a flag is literally flying it). But the expression, with its vivid imagery and connotations of success, has obvious appeal, and people duly broadened it to refer to achievements unaccompanied by flag-flying.
A related expression, also of naval pedigree, is to sail [or fight] under false colours, synonymous with under false pretences. It refers to an old seafaring trick associated with pirates but not limited to them, who misrepresented their identity by hoisting ‘friendly’ flags, and so were able to get close enough to a target ship to catch its crew unawares. An article at National Geographic describes how Blackbeard used the strategy:
The pirates often determined a ship’s nationality first. Then they raised that country’s flag on the pirate ship so they appeared to be friendly. Now able to draw close to the unsuspecting ship, the pirates hoisted Blackbeard’s flag only at the last moment.
As with flying colours, doing something under false colours soon began to be used figuratively to describe other acts of deception used to gain an advantage. This opinion piece in the Guardian, for instance, says a political party ‘under false colours’ concealed a shift to the right. The metaphor was deliberately selected to imply dishonourable guile.
Language has a tendency to become ever more abstract, obscuring its concrete roots. Colours, representing flags, representing identity, is used in ways far removed from its maritime origins. But by tracing its lineage we can refresh the metaphor and narrow the distance to our linguistic past.

Nice post, Stan; I love these ‘colourful’ (ouch) expressions. English is rammed with naval metaphors, presumably a result of the nation’s seafaring past (and present). Another nice expression deriving from ships’ use of flags is ‘nail (or pin) your colours to the mast’: to say clearly and publicly who you support or what you think about something; unlike the dastardly pirates with their false colours. They, of course, only ‘show their true colours’ at the last minute; and the negative connotation still clings to those who unwittingly reveal their real personality, especially when it is less pleasant than people have been led to believe.
Thanks, Liz. Nailing one’s colours to the mast is another good example, closely related to the two in the post. I don’t think I’ve ever used it, but I’ve always enjoyed the vividness of the imagery. I’m sure you’re right about the country’s past generating its boiunteous naval metaphors; it would be interesting to compare them with those of other such historically seafaring nations.