Clean Rom is one of the biggest Sense based roms for the HTC One M8 with more than 120,000 views for the Verizon variant alone. If you wanted to theme this rom you would be mostly out of luck since this is a Sense rom and it does not include the theme engine from Cyanogen Mod. Theme developer "Punka-res.apk" has taken matters into his own hands, and has created more than 18 custom themes for the Clean Rom on the HTC One M8. The theme is a dark theme. You can change the color scheme in settings/personalize. There are several different color schemes to choose from including Dark Grey, Blue, Green, Orange, Red, Purple, Yellow, Garnet, Green, Cyan, Pink, Tan, Brown, Gold, Pink Red, and more. Head to the link below for the download and flash in recovery.
Via XDA