Every daytime lighting condition can provide an opprotunity to enhance your vision by choosing the right kind of sunglasses. Overcast days, whether it's bright or dim, still require UV protection, especially if you are enjoying an outdoor activity like running, biking, skiing, or water sports. Since the amount of light is decreased when it is overcast or cloudy be sure to have a pair of sunglasses that allow a bit more light to come through. The Visible Light Transmission (VLT) should be anywhere from 25 to 50% under these conditions.
The classic sunglass lens color for these conditions is in the YELLOW family. True yellow, amber, orange, and yellow-green all tend to brighten objects in so-called "flat light" circumstances. These colors enhance contrast when bright sunlight is not available, increasing your perception of the environment. All of these lenses are great for Sporting Clays and hunting, and goggles with these colors work great if you are skiing or boarding in overcast conditions.