I've used white appliance touch-up paint as well as a white paint marker on my blue guns which seemed to work well. Not so much so on my stainless guns. I picked up some cheap reddish-orange nail polish at Walmart for use on those, but it didn't work too well-- not bright enough. I guess model paint or jig-and-lure paint would be better, I'll have to pick some up. I don't particularly like zombie green, but it seems like that might give more contrast than red orange or yellow.