Sunglass for men/women (lens):
Color of the Sunglass lens can vary by style, fashion, and purpose, but for general use, green, grey, yellow, or brown is recommended to avoid or minimize color distortion which would be dangerous when, for instance, driving a car. 
Gray lenses are considered neutral because they do not enhance contrast or distort colors. Sunglass with Brown and green lenses cause some minimal color distortion, but have contrast-enhancing properties. Red lenses are good for medium and lower light conditions because they are good at enhancing contrast but causes color distortion. Orange and yellow lenses have the best contrast enhancement at depth perception but cause color distortion. Yellow lenses are commonly used by golfers and shooters for its contrast enhancement and depth perception properties. Blue and purple lenses offer no real benefits and are mainly cosmetic.
Clear lenses are used typically to protect the eyes from impact, debris, dust, or chemicals. Some sunglasses with interchangeable lens have optional clear lenses to protect the eyes during low light or night time activities. Debates exist as to whether "blue blocking" or amber tinted lenses may have a protective effect. Blue blocking sunglasses typically also block some light of other colors to function well in full sunlight. Some low blue glasses are for use inside at night to avoid suppression of the sleep promoting hormone melatonin. They provide enough light so normal evening activities can continue.
Some modelshave polarized lenses (made from Polaroid or a similar material) to reduce glare caused by light reflected from polarizing surfaces such as water as well as by polarized diffuse sky radiation (skylight). This can be especially useful when fishing, as the ability to see beneath the surface of the water is crucial.
Gray lenses are considered neutral because they do not enhance contrast or distort colors. Sunglass with Brown and green lenses cause some minimal color distortion, but have contrast-enhancing properties. Red lenses are good for medium and lower light conditions because they are good at enhancing contrast but causes color distortion. Orange and yellow lenses have the best contrast enhancement at depth perception but cause color distortion. Yellow lenses are commonly used by golfers and shooters for its contrast enhancement and depth perception properties. Blue and purple lenses offer no real benefits and are mainly cosmetic. Clear lenses are used typically to protect the eyes from impact, debris, dust, or chemicals. Some sunglasses with interchangeable lens have optional clear lenses to protect the eyes during low light or night time activities. Debates exist as to whether "blue blocking" or amber tinted lenses may have a protective effect. Blue blocking sunglasses typically also block some light of other colors to function well in full sunlight. Some low blue glasses are for use inside at night to avoid suppression of the sleep promoting hormone melatonin. They provide enough light so normal evening activities can continue.
Some modelshave polarized lenses (made from Polaroid or a similar material) to reduce glare caused by light reflected from polarizing surfaces such as water as well as by polarized diffuse sky radiation (skylight). This can be especially useful when fishing, as the ability to see beneath the surface of the water is crucial.
A mirrored coating can also be applied to the lens. This mirrored coating reflects some of the light when it hits the lens before it is transmitted through the lens making it useful in bright conditions. These mirrored coatings can be made any color by the manufacturer for styling and fashion purposes. The color of the mirrored surface is irrelevant to the color of the lens.
Any of the above features: color, polarization, gradation, and mirroring, can be combined into a set of lenses for a pair of sunglasses. With the introduction of office computing, ergonomists can recommend mildly tinted glasses for display operators to increase contrast. Corrective lenses can be darkened to serve the same purpose, or secondary clip-on dark lenses can be placed in front of the regular lenses. Flip-up glasses feature a dark lens that can be flipped up when not in use. Some lenses gradually darken with bright light and lighten in darkness; these are known as photochromic lenses.
Sunglass lenses are made from either glass or plastic. Plastic lenses are typically made from acrylic, polycarbonate, or CR-39. Glass lenses have the best optical clarity and scratch resistance, but are heavier than plastic lenses. They can also shatter or break on impact. Plastic lenses are lighter than glass lenses, but are more prone to scratching. They do however, offer more resistance to shattering than glass. Polycarbonate lenses are the lightest, and are also almost shatterproof, making them good for impact protection. CR-39 lenses are the most common plastic lenses, due to their low weight, high scratch resistance, low transparency for ultraviolet and infrared radiation, and other advantageous properties. For sunglasses that also include vision correction, see also corrective lens.
Any of the above features: color, polarization, gradation, and mirroring, can be combined into a set of lenses for a pair of sunglasses. With the introduction of office computing, ergonomists can recommend mildly tinted glasses for display operators to increase contrast. Corrective lenses can be darkened to serve the same purpose, or secondary clip-on dark lenses can be placed in front of the regular lenses. Flip-up glasses feature a dark lens that can be flipped up when not in use. Some lenses gradually darken with bright light and lighten in darkness; these are known as photochromic lenses.
Sunglass lenses are made from either glass or plastic. Plastic lenses are typically made from acrylic, polycarbonate, or CR-39. Glass lenses have the best optical clarity and scratch resistance, but are heavier than plastic lenses. They can also shatter or break on impact. Plastic lenses are lighter than glass lenses, but are more prone to scratching. They do however, offer more resistance to shattering than glass. Polycarbonate lenses are the lightest, and are also almost shatterproof, making them good for impact protection. CR-39 lenses are the most common plastic lenses, due to their low weight, high scratch resistance, low transparency for ultraviolet and infrared radiation, and other advantageous properties. For sunglasses that also include vision correction, see also corrective lens.