I personally don't place any stock on the name on the label; it's about the individual coat and how it feels on you! Of course, quality is important But I wouldn't paint all the coats in once store with the "frumpy" label.
I have seen really cute trenches in dark purples and plaids ... I have a trench in a deep pink/purple colour ... I don't think they have to be black or beige. I really want an amazing red trench, but I haven't been able to find one.
I say if it works for you, any colour is good Some colours are less practical - ie: white; but hey, if you can keep it clean, yay!