Поменять цвет линии графика через checkBox - C#

private void Form2_Load(object sender, EventArgs e)
        {
            GlobalSettings.radioButton1 = 0;
            GlobalSettings.radioButton2 = 0;
        }
 
        private void button1_Click(object sender, EventArgs e)
        {
            if (GlobalSettings.radioButton1 == 1)      (????)     = System.Drawing.Color.Blue;
            if (GlobalSettings.radioButton2 == 1)       (????)    = System.Drawing.Color.Red;