show someone’s true colours

(verb) to show the real nature or characteristics of a person

Example Sentences:

Everyone thought Bill was a nice guy, but he showed his true colors when he was really rude to the waitress at his birthday party.

The young woman wanted to show everyone her true colours when she decided to volunteer.

My roommate started showing me her true colours about six months after we moved in together. She’s so messy!

Media:

Similar idioms:

1. show-off
2. show up
3. pass something with flying colours
4. show off
5. get out of something
6. under one’s breath
7. show someone the ropes
8. show off