When clay shooting, it is always advisory to wear glasses to protect your eyes from fragments of broken clay. They are also extremely useful for improving visibility in different outdoor conditions. A variety of coloured lenses are used to help different coloured clays show up better in specific conditions, lighting or backgrounds. I use Beretta or Pilla shooting glasses and generally use a 22N lens now the weather is nice and light.
The Beretta Race Glasses are a particular favourite of mine.
They offer an all-round lens, which shows up orange clays very well against a background and vision for black clays is not compromised. They are have a rather wide lens, which stops light from flooding in.
During the winter when the lighting is poor and rather dull, I mostly use a clear lens with a slight tint of green, allowing most light to enter your eyes.
There are many different brands and models of shooting glasses, some much better than others, mainly based on the clarity of the lenses. You can tell the difference between cheap and expensive shooting glasses rather easily. Cheap shooting glasses can perform a basic job and are often a popular choice for people who are not keen to invest a lot of time or money in shooting. However, those who are regular shooters and particularly those who compete find that high quality shooting glasses are a great investment of money as the difference in protection and performance is vast.