Typically I chop up a head of romaine, swish it around in some cool water, then spin it dry. The swishing water ends up very green, however. I'm wondering if it's getting doused in some dye prior to purchase, or if I'm preparing it wrong and leeching out the nutrients?
I never heard of lettuce dye, I wouldn't panic with that. You are not loosing nutriments either, like Michael said it might be chlorophyll, wich would explain the green color, but you are not losing nutriments for sure. I often have green water too, it's really not a big deal, don't worry!