Why is this important when selecting polarizing glasses? To better see the mirror-like sides of a flats fish, you need to build as much contrast as possible between the fish and the area it is swimming over. For that reason, polarizing glasses come in many colors. Any hunter who has worn what we call shooting glasses knows that on rainy or low-light days these brilliant yellow lenses act is if the lights have been turned on. That is because the yellow dramatically increases contrast. The best polarizing lenses, I believe, will have some of this yellow in them. In fact, I use similar yellow polarizing lenses on overcast or rainy days. But on a sunny day the yellow lenses are too bright for almost anyone, so tan, copper or a darker tint is added. This reduces eyestrain, but the yellow builds contrast.