With summer doing it's job with giving you natural highlights, you might just let nature take its course with your color. Or you can give nature a little help and add some salon made higlights or just go all out lighter. Many celebrities have taken this route, including famously dark haired Kim Kardashian and A lister Angelina Jolie. Lightening your hair brightens up your face and is a good summery look. You do have to beware of going too light beause that can wash you out.
If you are feeling lucky, go two to three shades lighter than your natural color.