While the primary purpose of brown or grey-tinted lenses is to block all colors of light, to lessen eye-strain in harsh lighting conditions, Orange and Yellow tinted lenses have a more specific purpose.  Those lens tints make one’s vision crisper and sharper by blocking blue light, which is the cause of haze.  For this reason, these lenses are often referred to as “blue-blockers” and are the preferred tint for shooting glasses, and for dawn, twilight or cloudy-day outdoor activities.