求解枚举的问题 为什么错我

public class lianxi8 {

public static void main(String[] args) {

ColorEnum colorEnum = ColorEnum.blue;

        switch (colorEnum) {

        case red:

            System.out.println("color is red");

            break;

        case green:

            System.out.println("color is green");

            break;

        case yellow:

            System.out.println("color is yellow");

            break;

        case blue:

            System.out.println("color is blue");

            break;

        }     

}

}