Holy crap, someone else is having the same issues as me. I posted about this on the Dell forums and the guy said it was cause I was using a Mac as an input
I saw your thread on the dell forum. That dell rep is a complete idiot.
Custom color will break on that last one as well. I thought it worked on the last one I received as well, but it broke after a while just like the others.
You are correct. It worked right for several days and then turned completely green.