A couple of thoughts that occurred to me after the initial flames of anger and disappointment died down:
-There was only a small core group of elders who founded the village. The population at the time of the movie appears to be 60-100 people. If they continue to be isolated for another two or three generations, there's going to be some serious inbreeding. I'm talking flipper babies, people.
-So red is the "bad color." Nothing in the entire town is red. There's no technology and it's apparently an agrarian society that relies heavily on human power to get work done - a state of affairs that privileges physical strength. How many generations would it take for women (cursed monthly with manifestations of the "bad color") to be utterly subjugated? They appear to have political equality at present (which struck me as anachronistic when we first saw the elders' meeting), but how long can that last?