You get the chance to complete the Legionaries Loop, which is two to three obstacles, being harder or longer and one of them being "something new, unique and badass" though doing this also gives you a bypass on the electroshock therapy which is something worth utilising.
I'm hoping that I'll be able to get myself one of each colour headband before I hit the black headband, I also can't wait to see people sporting the various colours at the event site.
If you want to, have a look at the video that I saw.
Since I started writing this post, I found this post which outlines the new headbands. http://obstacleracingmedia.com/editorial/mudder-legion-unleashes-rainbow-warriors/