// ColorRGB.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <stdio.h>

int _tmain(int argc, _TCHAR* argv[])
{
    unsigned char red, green, blue;
    while (1)
    {
        printf("Please input the three RGB values: \n");
        scanf_s("%d%d%d", &red, &green, &blue);
        printf("The result is: #%02X%02X%02X\n\n", red, green, blue);
    }
    return 0;
}

运行效果：

上述程序在编译成Release版本后无法读取第二个green的颜色值，所以最好把unsigned char改成unsigned int：
// ColorRGB.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <stdio.h>

int _tmain(int argc, _TCHAR* argv[])
{
    unsigned int red, green, blue;
    while (1)
    {
        printf("Please input the three RGB values: \n");
        scanf_s("%d%d%d", &red, &green, &blue);
        printf("The result is: #%02X%02X%02X\n\n", red, green, blue);
    }
    return 0;
}