I googled just now and find out there is some products of sunglasses with transparent lenses. And I can see this kind of products in movies that the hero wearing a pair of glasses which can turn dark automatically as he walked into some bright circumstances. There are some such products, but they are not familiar to us and they are not so popular. Contact lenses are transparent, and they can also provide protection from UV radiation to some extent. But they are not as good as sunglasses. Actually sunglasses with various colored lenses are more fashionable and cooler. Brown lens is the best choice recommended, because it could provide 100% protection from UV rays. Grey is a fashionable choice, and it also can provide fully protection too. If I were you, I would rather choose sunglasses with colored lenses.