Here is what I know, currently there is only the Maximus VIII Hero Alpha and the Maximus VIII Formula which include RGB headers to control external RGB LED strips. The Alpha has two headers which can be independently controlled, the Formula has just one. I'm sure that more boards will follow as RGB accent lighting seems to be the latest craze.
For those that have one of these boards and an eligible Phanteks case purchased before March 1st 2016 there is a promotional offer for a free LED lead that will enable the case accent lighting to be controlled from the motherboard. Pretty cool!
The promotional offer details an be found here....
http://phanteks.com/PH-CB_RGB4P/promo.htmlAnd here is an article providing more detail on the actual lead....
http://www.pureoverclock.com/2016/02/phanteks-rgb-led-adapter-launch/It looks to be retailing for approx £4.