This really crops up with shooting glasses. They have many colors that are supposed to enhance either target colors or definition. Everyone's eyes are different and they see colors and combinations of colors differently. Choosing the right one makes both stationary and flying targets easier to define and see. Here is a perfect example. Purple is supposed to block green and enhance orange. Many sporting guys swear by them in the woods. When I put them on the target turns the exact same color as the sky and totally disappears. Choosing the right color can enhance any target, rifle, shotgun, or pistol.