为什么枚举无法在JAVA中解决？

public enum Color {
    RED, GREEN, BLUE
}

public enum Color {
    RED("FF0000"), GREEN("00FF00"), BLUE("0000FF");

    private String code;

    Color(String code) {
        this.code = code;
    }

    public String getCode() {
        return code;
    }
}

public interface Color {
    String getCode();
}

public class Red implements Color {
    public String getCode() {
        return "FF0000";
    }
}

public class Green implements Color {
    public String getCode() {
        return "00FF00";
    }
}

public class Blue implements Color {
    public String getCode() {
        return "0000FF";
    }
}

public class Color {
    public static final String RED = "FF0000";
    public static final String GREEN = "00FF00";
    public static final String BLUE = "0000FF";
}