How can I make a control occupy all the client area of a form

private void Form1_Load(object sender, System.EventArgs e)
{
  Bitmap newBmp = new Bitmap(100, 100);
  Graphics g = Graphics.FromImage(newBmp);
  g.FillRectangle(new SolidBrush(Color.Red), 0, 0, 33, 100);
  g.FillRectangle(new SolidBrush(Color.White), 34, 0, 33, 100);
  g.FillRectangle(new SolidBrush(Color.Blue), 68, 0, 33, 100);
  pictureBox1.Image = newBmp; //pictureBox1 was dropped on the form
}