Preheat the oven to 350 F. In a large bowl, mix together cake mix, oats, eggs, and vegetable oil until smooth. Divide the cookie dough into three bowls, and mix one with purple food coloring, one with orange, and one with green.
In a shallow dish, combine granulated sugar and ground cinnamon. Take a small amount of each cookie dough and roll into balls. Roll each one into the cinnamon sugar mixture.
Place cookies onto a large ungreased baking sheet at least 2-inches apart. Bake for 10-12 minutes.