The green bins are for yard trimmings. The blue bins are for recyclable items. The black bins are for (non toxic) trash. This system has been in place for many years. So when our neighbors, Mr. and Mrs. Loud,* stuffed their green and blue bins full of old carpeting, they were the only ones to be surprised that the bins weren't emptied. "I didn't know," Mrs. L claimed later that morning. Luckily for her, the truck handling black bins had not yet arrived. So she waited by the bins, told the driver of the trash truck she had made a "mistake", and got him to empty these. It's a good thing, too, because the Louds' excess trash has a way of mysteriously appearing in other people's bins in the middle of the night.
*Not their real name, but an accurate description.