哪位大哥帮忙找一下下面程序的错误：
我调试时提示：
错误    2    error C2676: binary '++' : 'wmain::color' does not define this operator or a conversion to a type acceptable to the predefined operator    c:\documents and settings\颩，無心\my documents\visual studio 2005\projects\enum\enum\enum.cpp    15   


这是个枚举型的例子，书上说枚举型可以自加运算，但这儿却出错；我用的VS2005调试的；好像VC6.0也是同样的错误；


#include "stdafx.h"
#define n "%-10s"

void main()
{
    enum color{red,yellow,blue,white,black};
    enum color i,j,l,pri;
    int m,loop;
    m=0;
    for(i=red;i<=black;i++)
        for(j=red;j<=black;j++)
            if(i!=j)
                for(l=red;l<=black;l++)
                    if((l!=i)&&(l!=j))
                    {
                        m=m+1;
                        printf("%-4d",m);
                        for(loop=1;loop<=3;loop++)
                        {
                            switch(loop)
                            {case 1:pri=i;break;
                            case 2:pri=j;break;
                            case 3:pri=l;break;}
                            switch(pri)
                            {
                            case red:printf(n,"red");break;
                            case yellow:printf(n,"yellow");break;
                            case blue:printf(n,"blue");break;
                            case white:printf(n,"white");break;
                            case black:printf(n,"white");break;
                            }
                        }
                        printf("\n");
                    }
}

还是不行，同样的错误，好像是关于枚举型自增运算的问题

用vc6.0也不行吗？我用VC6.0也不行，同样的错误，当然头文件改成#include"stdio.h"了。

谁能帮我解释一下提示错误的意思吗：
错误    2    error C2676: binary '++' : 'wmain::color' does not define this operator or a conversion to a type acceptable to the predefined operator