Not color, quality. It is not so much the color or shade of the sunglasses but the quality of the lens in protecting you from uva and uvb sunlight. Look for high quality or brand name sunglasses that states 100% uva and uvb protection.
None. There is no color of sunglass that harms your eyes, although they may alter contrast sensitivity or perception of true colors. What can damage your eyes is the use of darkly colored sunglasses that do not have a complete uv block down to 400 nm. By wearing dark sunglasses without a uv-block, your pupil dilates and lets in the dammore damaging ultraviolet rays that can cause cataract or retinopathy.
Not a Color, UV. Make sure that your sunglasses block 100% of uv light, and many doctors feel that blue blockers are also important, so block anything below 400nm.