Protection from the sun's ultraviolet rays is colorless, so choosing the shade of your shade's frame and lenses is strictly a style decision. This photo features Kate Spade's Pauline sunglasses.

You're staring at a case full of sunglasses, and all those sunglasses are staring right back at you.

Which one will you try on? What style is best suited for your face?

There are multiple factors to consider when shopping for sunglasses, says Carol Norbeck, vice president of special projects for Silhouette, including the shape and proportions of your face, and your personal style.

To pick the best pair for you, Norbeck recommends this little exercise: Draw the shape of your face -- short and round, long and narrow or even triangular -- on a piece of paper. Next draw the opposite shape glasses on the face. That's probably the shape for you.

For example, if your face is a long and narrow oval, draw boxy glasses; for a short and round face, draw rectangular glasses; and for a face with sharp features, try softer, rounder glasses.

When it comes to choosing the color of both the frames and the color of the lens, Norbeck advises sticking to the guidelines you already know.