be sailing under false colours
be sailing under false coloursBRITISH
If someone or something is sailing under false colours, they are deliberately deceiving people. Note: A ship's colours are its national flag. This report sails under false colours. It claims to be a fair and rigorous examination of the issue, but it is no such thing. Note: When pirate ships spotted a treasure ship, they often took down their own flag and raised the flag of a friendly nation, in order to get close enough to the ship to attack it.