Students decorate the classroom with balloons, and hang up the balloons in the order of red, yellow, green, and blue. What color is the 40th balloon?
同学们用气球装饰教室，按红、黄、绿、蓝的顺序把气球依次挂起来，请问第40个气球是什么颜色的？
<result>40</result>