1. It's not "brown", it's "boiled caramel", a definition by Noctua itself.
2. Their trade mark color scheme is of such combination because Noctua's founder is actually a big sweet-tooth and loves caramel very much, so they created this color scheme out of his preferences. Meaning that this color scheme won't go away for a looooooong time. So deal with it and live with it. %)
3. It looks awesome in any case, it's a very calm, eye-candy (geddit?) color. Screw all haters.