C#中更改groupbox的邊框的顏色

e.Graphics.Clear(groupBox1.BackColor);

e.Graphics.DrawString(groupBox1.Text, groupBox1.Font, Brushes.Blue, 10, 1);

e.Graphics.DrawLine(Pens.Black, 1, 7, 8, 7);

e.Graphics.DrawLine(Pens.Black, e.Graphics.MeasureString(groupBox1.Text, groupBox1.Font).Width + 8, 7, groupBox1.Width - 2, 7);

e.Graphics.DrawLine(Pens.Black, 1, 7, 1, groupBox1.Height - 2);

e.Graphics.DrawLine(Pens.Black, 1, groupBox1.Height - 2, groupBox1.Width - 2, groupBox1.Height - 2);

e.Graphics.DrawLine(Pens.Black, groupBox1.Width - 2, 7, groupBox1.Width - 2, groupBox1.Height - 2);