Winnie the Pooh, Piggy, Donkey and Rabbit once went to pick berries in the forest. Each of them had trousers of different colour: red, yellow, blue and green. Donkey never puts on yellow trousers, and Rabbit never takes on red ones. Winnie the Pooh and the one in green trousers have already eaten sweet raspberry. Rabbit shows the blackberries he gathered to the one wearing yellow trousers. The one in green trousers calls Donkey and Rabbit to show them nice raspberry-canes. What color trousers does each wear?