The reason we chose to go with the brown is because as a graphic designer, I understand how colors can look with a different color wash over the film. The inside Hoth coloration has a definite blue hue, just look at Chewbacca, he even looks blue in the hanger. We also know that you can shine a blue light on a dark brown to make it look navy blue, but you would have to shine a brown light on a navy blue to get it even close to brown, and there would be no cause for any brown lighting in Hoth. Also, if you look at the scene outside when they shoot the probe droid, it is a natural light, and it looks like a very dark brown. And finally, if you look at all the outfits of the other rebels, they all have earthtone outfits with blue gray boots. Han's Parka doesn't stand out as a total different color from the rest, it blends in with the other earthtones...