Inspire yourself with Asphalt Green.*
I changed as much as I could to Marshmallow resources, my theme has a beautiful wallpaper and it is grey with green.
I have only tested it on one Xperia device, so if there is a problem just let me know at: hello.justinwaterfall@gmail.com
NOTE: Some applications can force a different colour onto the navigation bar.
*This theme can only be used on Xperia devices.