Is your heart set on GFG? There are loads of other designs you can make using the hexies where you can mix up your mediums lights and darks. I am a fan of forming the diamond shape with hexis.
Like the first quilt in this blog, but please scroll down for some amazing takes on hexi quilts that should inspire you to continue on.
http://suegarman.blogspot.com/2013_05_01_archive.html