Never heard of the marigold thing...darker orange yolks are supposed to, as far as I'm aware, signal a higher nutrient content, and this marigold thing just sounds like a way of someone essentially "dying" the yolks so that people think the eggs are superior.
Anyways, I always look for chickens that have lots of room to run around, and some grass. Here in AZ you find lots of people raising chickens in a really crowded dirt lot-type things. I wouldn't worry too much about organic--if the chickens are running around eating bugs, then I would think that's the most important thing, and a little bit of conventional feed won't be a big deal.
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