Further, I'd think the brain must value that extra information, lest it'll just ignore it. If a kid is told that oranges are orange and bananas are yellow, wil

Further, I'd think the brain must value that extra information, lest it'll just ignore it. If a kid is told that oranges are orange and bananas are yellow, will it actually develop a sense that there are different shades? Otoh, the ability to pick the bananas which are just perfectly ripe or the sweetest strawberries might come in handy. Oranges, bananas and strawberries might be bad examples as to some degree trichromats can perform such feats, but there might be other fruits and vegetables for which this would be more difficult.