This photo was of Kelly during her time during and after American Idol. It is my understanding that the highlights and low lights were clip in extensions strands which were positioned to give Kelly the unique hues. I heard she also had some of the hair around her hairline and interior lifted and then colored 2 shades lighter.
Over the years since appearing on American Idol Kelly has gone through major transitions with her hair styles, colors and lengths. I loved her hair best when she went completely blonde.