Code

  //creating timer
  Timer tm = new Timer();
  //at button click event setting timer interval to 5000 and enabling the timer
        
        private void btnClick_Click(object sender, EventArgs e)
        {
            tm.Interval = 5000;
            tm.Enabled = true;
        }
 
  //writing timer event handler at tick event of timer.
        private void tm_Tick(object sender, EventArgs e)
        {
            this.BackColor = Color.Blue;
            tm.Enabled = false;
        }
 
  //at form load event creating timer event handler
        private void Timer2_Load(object sender, EventArgs e)
        {
            tm.Tick += new EventHandler(tm_Tick);
        }

 Screenshot

The back color of form changed after 5 seconds of a button click.

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