Mike your right this blank is root beer color. I was told by Sage the factory rods were made with the dark green main wrap and dark green NCP for trim. ( code # 5896A 5896 NCP Gudebrod) It would be nice if someone could send me a picture of the factory rod with the green wrap.
I also was thinking of the brown color and light brown or tan color trim, again pictures are worth a thousand words. I guess the browns would blend in with the color of the blank. Green? Brown ?
I usually do my trim in either metallic or NCP. A non-coated thread will just sort of disappear into the other wraps and blank, so if you're going to bother doing a trim wrap it might as well be something that stands out.
If you plan to keep the rod and fish the heck out of it then use purple if it pleases you. That is all that is important. Otherwise do as the guys have advised. Just don't do red. Gawd, red wraps drive me crazy. It's personal thing.