Ok, my primary chaos army at this time is black legion. (I plan to do a dedicated deathguard/nurgle army at a later time) I want to add a squad or two of plague marines, but I can't decide on a color to do them in. Here are the two ideas I'm looking at....
1) Standard nurgle/plague marine greens and browns (think goatboys quick and dirty plague marine guide on dakka) but with a black shoulder pad and perhaps the black legion decal with gold shoulder trim.
2) Standard black legion colors, with lots of muted gray added in to represent wear and decay on the armor.
A few things to bear in mind....when I do my nurgle army, it will follow the standard green/brown theme...so I'm trying to go in a different direction with these guys. Also, I'm using the standard
GW plague marines, no
GS sculpting or custom models in my army at this time...I'm just not that good yet!

Also, if you have any ideas or pictures that are all together different from what I've posted above do feel free to share!