[show one's colors] {v. phr.}
1. To show what you are really like.
* /We thought Toby was timid, but he showed his colors when he rescued the ponies from the burning barn./
2. To make known what you think or plan to do.
* /Mr. Ryder is afraid that he will lose the election if he shows his colors on civil rights./* /We would not help Jim until he showed his colors./