What is the origin of the idiom "chase rainbows" and when to use it?

The origin of the idiom "chase rainbows" goes back to the ancient Greek myth of Iris, the goddess of the rainbow, who was said to use the rainbow as a bridge between the gods and mortals. Today, the idiom is commonly used to describe a situation where someone is pursuing a goal or objective that is unlikely to be achieved, often because it is based on unrealistic expectations or impossible desires. The idiom implies that the person's efforts are futile and that they should focus on more achievable goals or objectives.