Lens color or degree of darkness does not insure UV protection. The coating that blocks UV radiation is clear, so a darker lens isn’t necessarily more effective than a lighter one. But hue does play an important role in color perception. Certain tints are preferable for different uses.
Personal preferences often drive lens color decisions but it is helpful to know how each lens tint performs differently in various light conditions to enjoy optimal performance from your i-gogs sunglasses.