Выбор цвета эллипса через RadioButton-ы

      private void pictureBox1_Paint(object sender, PaintEventArgs e)
         {
            if (radiobutton1.Checked == true)
            {
                Pen blackPen = new Pen(Color.Black, 3);
                Rectangle rect = new Rectangle(0, 0, 150, 100);
                e.Graphics.DrawEllipse(blackPen, rect);
            }
            else if(radiobutton2.Checked == true)
            {
                Pen blackPen = new Pen(Color.Green, 3);
                Rectangle rect = new Rectangle(0, 0, 150, 100);
                e.Graphics.DrawEllipse(blackPen, rect);
            }
        }
......

private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
    Pen pen;
    if (radiobutton1.Checked)
        pen = new Pen(Color.Black, 3);
    else
        pen = new Pen(Color.Green, 3);
    Rectangle rect = new Rectangle(0, 0, 150, 100);
    e.Graphics.DrawEllipse(pen, rect);
}
 
private void button1_Click(object sender, EventArgs e)
{
    pictureBox1.Invalidate();
}
 
private void radiobutton1_CheckedChanged(object sender, EventArgs e)
{
    pictureBox1.Invalidate();
}
 
private void radiobutton2_CheckedChanged(object sender, EventArgs e)
{
    pictureBox1.Invalidate();
}

pictureBox1.Invalidate();

private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
    SolidBrush brush;
    if (radiobutton1.Checked)
        brush = new SolidBrush(Color.Black);
    else
        brush = new SolidBrush(Color.Green);
    Rectangle rect = new Rectangle(0, 0, 150, 100);
    e.Graphics.FillEllipse(brush, rect);
}