Do something till you are blue in the face
Definition 1 of 1
Pro Tip 1/3Persistence imagery
The phrase evokes the image of someone persisting to the point of exhaustion. 
He practiced the piano till he was blue in the face.
Pro Tip 2/3Emotional frustration
It implies a sense of frustration or futility in the effort. 
She tried to solve the puzzle till she was blue in the face.
Pro Tip 3/3Not literal
It's an idiom, so don't take it literally. It's not about actual color change. 
They debated the issue till they were blue in the face.