红绿灯的设计

int i =0；
private void timer1_Tick(object sender, EventArgs e)
        {
            if (i == 0)
            {
                this.red.BackColor = Color.Red;
                this.yellow.BackColor = Color.Black;
                this.green.BackColor = Color.Black;
                i = 1;
            }
            else if (i == 1)
            {
                this.red.BackColor = Color.Black;
                this.yellow.BackColor = Color.Yellow;
                this.green.BackColor = Color.Black;
                i = 2;
            }
            else if (i == 2)
            {
                this.red.BackColor = Color.Black;
                this.yellow.BackColor = Color.Black;
                this.green.BackColor = Color.Green;
                i = 0;
            }
            

        }

1 private void Form1_Load(object sender, EventArgs e)
2         {
3             this.red.BackColor = Color.Black;
4             this.green.BackColor = Color.Black;
5             this.yellow.BackColor = Color.Black;
6         }