I wear amber lens safety glasses from Tru Value Hardware. The amber color highlights the trail contrasts. (Same concept as shooters lenses). The other nice things are the arm angles can be adjusted to fit with your helmet just right, and the lenses wrap around the side. I think they cost about $9.50.
http://www.truevalue.com/product/Amber-Lens-Safety-Glasses/12142.uts?keyword=Safety%20glasses
When it gets below 20 degrees in the winter (I live in Michigan) I wear Smith ski goggles, rose color lenses, and they have vents so they don’t fog up.