Sorry, it drives me crazy when people lump all hunter judging as "political". I've been to too many judging clinics, I know several judges -some big names, and have sat in classes where I didn't know the riders and can often call who will walk away with a ribbon. Believe it or not, there is a standard that judges work from.
The main problem with non traditional colors is that in a sea of like clothed people someone who sticks out will stick out like a sore thumb and it is distracting and points all eyes on you mistakes and all. A judge I know (who travels practically every week to places like Wellington, Devon, Kentucky, etc) said that when she sees something untraditional that's the first thing she notices, not the quality of the horse and that's not what you want. That is also George Morris's problem with crazy bling and flash, that it takes away from the horse and the horse should always be the star of the show.
So to answer your question? Yes, rust is accepted and surpringly loved in the hunter circle, especially around the nostalgic crowds. :) I wear rust breeches periodically and get compliments. EVERY. TIME. You could show in greyish or more brownish breeches. But I wouldn't veer too far from those colors. As far as jackets go it's hard to veer too far from the traditional navy, black, grey, or even the occasional brown BUT I have been hearing from my friends in FL that there has been a surge in popularity of dark green coats this year! I don't think a color will necessarily cause you a penalization but you'd probably get the same reaction as a potential employer if you came into a job interview wearing non traditional colored suit. A funny look, some questions, and perhaps a question of whether or not you can deliver. If you want to make the best first impression you can, wear the traditional colors. If you honestly don't care and you're in it purely for the fun, then take a chance. Well, actually... just how crazy are we talking here?? :)