How to highlight button after click

@Sachin, it did work. However, I am trying to use this code as well

private void btnUserUpdate_Click(object sender, EventArgs e)
        {
            User_Update x = new User_Update();
            x.Show();
            this.Hide();
        }

1. private void BtnAdminLogin_click(object sender, EventArgs e)  
2. {  
3.     Button btn = sender as Button;  
4.     btn.BackColor = Color.Yellow;  
5.    leftbtnAdmin.BackColor = Color.Yellow; //left side button  
6. }