程式碼如下：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication2
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            this.timer1.Interval = 100;
            this.timer1.Enabled = true;
            label1.Text = DateTime.Now.ToString();
        }

        private void time(object sender, EventArgs e)
        {
            label1.Text = DateTime.Now.ToString();
        }

        private void 黃色ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            label1.ForeColor = Color.Yellow;
        }

        private void 黑色ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            label1.ForeColor = Color.Black;
        }

        private void 綠色ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            label1.ForeColor = Color.Green;
        }

        private void 紅色ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            label1.ForeColor = Color.Red;
        }

      
    }
    
}

 

效果如下：