Покрасить пользовательский контролл

internal class TriangleBtn : Button
  {
    protected override void OnPaint(PaintEventArgs pevent)
    {
      GraphicsPath g = new GraphicsPath();
      float h = this.Height;
      float w = this.Width;
      PointF[] pts = new PointF[] { new PointF(w / 2, 0), new PointF(0, h), new PointF(w, h) };
      g.AddPolygon(pts);
      this.Region = new Region(g);
      base.OnPaint(pevent);
    }
  }

triangleBtn3.BackColor = SystemColors.ControlDark;

public class PaintEventArgs : EventArgs, IDisposable
{
 
    public System.Drawing.Rectangle ClipRectangle {get;}
    public System.Drawing.Graphics Graphics {get;}
 
    // Other properties and methods.
}

protected override void OnPaint(PaintEventArgs e)
{
    // Call the OnPaint method of the base class.
    base.OnPaint(e);
 
    // Declare and instantiate a new pen that will be disposed of at the end of the method.
    using var myPen = new Pen(Color.Aqua);
 
    // Create a rectangle that represents the size of the control, minus 1 pixel.
    var area = new Rectangle(new Point(0, 0), new Size(this.Size.Width - 1, this.Size.Height - 1));
 
    // Draw an aqua rectangle in the rectangle represented by the control.
    e.Graphics.DrawRectangle(myPen, area);
}