Amber is the best solution, but red would be more acceptable if the OEMs didn't use it as license to cheap out and cosolidate and distill three functions (tail/stop/signal) into a single light source. Some of the older Chrysler products, like the minvans, and pickups are notable examples, with a single red lense with a clear cutout, and two bulbs, one for reverse, and one for everything else. Having discrete sources for each function would at least reduce the risk of potential confustion, even if they're all the same color.