I'm guessing (based on being a crafter, not an expert) that the actual color of the suit is a grey/brown taupe and possibly what we see on screen is the result of whatever photography is going on that day. I recall from the Hobbit movies that the camera was "bleeding" the reds out of the actors' faces, so the actors were over-made up with a lot of burgundy to counter the effect.
Then there's the problem of different dye lots and different costumes for actors and stunt people. Probably drives cosplayers and HT mad, if a color is a mix of shades. Anyway, I'm leaving my suits alone until I see enough pictures of the real thing (and even that is getting affected by lighting). Not that I ever blame anyone for modding a figure to get the look they want. Because season 2, Episode 1 that had a lot bright sunlight, the suit looked chocolate brown to me. Maybe one day the costumers can talk without getting sued.