Final answer:
To "shout something until you are blue in the face" means that you are exerting yourself with no results. It's a metaphor for futile effort and frustration, as if one could shout to a degree of turning blue without any change in circumstance.
Step-by-step explanation:
If you shout something until you are blue in the face, it means you are wasting your efforts because you will get no results. This expression is often used to signify an extreme level of personal exertion with an emphasis on the fruitlessness or ineffectiveness of that effort, regardless of how much energy is expended or how fervent the attempt is. It is not that you are actually turning blue; rather, the phrase is a colorful metaphor suggesting that someone might metaphorically shout to such a degree that they could turn blue from the effort, just as if they were deprived of oxygen.
This saying does not literally indicate that a person is experiencing physical exertion up to the point of oxygen deprivation, which can cause an actual change in face color as seen in medical emergencies. Instead, it underscores the futility and possible frustration associated with trying to achieve or change something despite stubborn resistance or unyielding obstacles. It emphasizes the pointlessness of continuing to shout or argue because it will not lead to a desired change or outcome.