Most online eyewear providers feature a catalog that shows the frames they offer in detail. You can view each available color and read a description of the frames' features, such as what material they're made of (plastic or metal, for example), or whether they have spring hinges.
You also need to decide what lens material and which coatings, if any, you want. Are polycarbonate, high-index or regular plastic lenses best for you? Do you need ultraviolet (UV) coating? What about an anti-reflective coating? Is a tint a good idea?