请用c语言实现：一个单词表存放了五个表示颜色的英文单词，输入一个字母，在单词表中查找并输出所有以此字母开头的单词，若没有找到，输出Not Found。要求用指针数组和二级指针实现。

#include <stdio.h>
#include <string.h>

#define MAX_LEN 20
#define COLOR_NUM 5

int main() {
    char colors[COLOR_NUM][MAX_LEN] = {"red", "blue", "green", "yellow", "black"};
    char letter;
    char **p_colors[COLOR_NUM];
    int i, j, count = 0;

    printf("Please input a letter: ");
    scanf("%c", &letter);

    for (i = 0; i < COLOR_NUM; i++) {
        p_colors[i] = &colors[i];
        if (colors[i][0] == letter) {
            count++;
        }
    }

    if (count == 0) {
        printf("Not Found\n");
    } else {
        printf("The colors starting with '%c' are:\n", letter);
        for (i = 0; i < COLOR_NUM; i++) {
            if ((*p_colors[i])[0] == letter) {
                printf("%s\n", *p_colors[i]);
            }
        }
    }

    return 0;
}