It originated from the color of the uniforms worn by loyal supporters of the Hanoverian monarchy in England during the 18th century. These uniforms were a deep blue color, and thus, "true blue" came to symbolize unwavering loyalty.
Here are some examples of how the idiom is used:
* "He's a true blue friend, always there to lend a hand."
* "The company has a long history of true blue customers who have been with them for decades."
* "She's a true blue patriot, always proud to represent her country."
The idiom "true blue" is used to describe someone or something that is dependable, trustworthy, and unwavering in their support or commitment.