I've had my issues with InStyle Magazine covers in the past (see here and here) but this cover really scares the hell out of me. Those eyebrows are just terrifying. They overwhelm Ms. Knightley's delicate face, and I refuse to believe they were there during the original shoot. No, those eyebrows had to be photoshopped in. I don't even think they used the photoshop program, they put those in with a Sharpie marker.
Please do not emulate these disaster brows. While I don't agree with people lightening their hair at home (leave highlights to the professionals), you can easily lighten your eyebrows at home using a facial hair bleach. Make sure to leave the bleach on for the shortest possible time (you can always reapply), and aim for a couple shades darker than the hair on your head.