// hook into control paint events change their appearance
// standard Button control does not have properties to control the 
// border size or color. In this code , you hook into the button’s Paint event and 
// modify its appearance.
private void ChangeButtonBorder(object sender, System.Windows.Forms.PaintEventArgs e) 
{
    // Hook into the paint event for myButton. Create a new graphics object
    // and paint a custom border around the button.
    
   System.Drawing.Graphics g = e.Graphics;
   
   int BorderWidth = 3;
   System.Drawing.Color BorderColor = System.Drawing.Color.Blue; 
   
   System.Windows.Forms.ControlPaint.DrawBorder( 
      g, e.ClipRectangle, BorderColor, BorderWidth, 
      System.Windows.Forms.ButtonBorderStyle.Solid, BorderColor, BorderWidth, 
      System.Windows.Forms.ButtonBorderStyle.Solid, BorderColor, BorderWidth, 
      System.Windows.Forms.ButtonBorderStyle.Solid, BorderColor, BorderWidth, 
      System.Windows.Forms.ButtonBorderStyle.Solid);
}