He's a Servant of Decay so he is infected by Nurgle's love, not necessarily willingly. He is basically untrained rabble, that crashed onto a war torn planet then is lead by religious fanatics straight into the enemy to die in droves. At least that is kinda my interpretation of the fluff behind their inclusion in an army. The rest of the army, besides the Zombies is Rebel militia so they will have modified military uniforms, I'm using English Uniform Brown for the uniforms, but with a healthy amount of black and of course purple.
Not so much red... Greens, browns, beiges, maybe even some oranges...
It is one of my larger project for the coming 12-16 months. I forget how many I need in the 1500 point army, but I plan to do a few more, maybe close to 50. That is how large a single squad can be, they are 4pts I think maybe less armed just like that with a token gun and hand weapon. The rules for them are in Imperial Armour 7.
Thanks for the comments. And yes I schemed up the blue-grey skin to show they are unhealthy but basically human. The zombies and any demons will look less well. I'm painting some Plaguebearers now but they can't appear in the same army list as these guys, but someday I'll do the mother of all battles and put all my Nurgle figures on one battletop. That isn't usually my style, my army isn't so portable and I don't currently own a car, but people always want me to come out so they can kill my pretty painted figures with their ugly unpainted ones.
Doesn't seem very fair to me. ;-)