COMMON If someone shows their true colours, they show their real character, often when this is bad. Note: A ship's colours are its national flag. Someone I had trusted now showed her true colours. Note: Verbs such as declare and reveal are sometimes used instead of show. Three months into the relationship, Rogers began to reveal his true colours. Note: You can also see someone in their true colours. The children started seeing him in his true colours for the first. Note: Once a pirate ship had got close to a treasure ship by `sailing under false colours', it then revealed its true identity by raising its own flag.