How to change the l background color of a tabcontro if a radio button is checked in C# win form

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C#

Good day please i am building a cbt app, i built a tabcontrol,tabpage,label and radio button from scratch but i want the tabcontrol to be red but whenever i click the radio button the tabcontrol should be green but i am confused because the tab control only get colored if i use the drag and drop tabcontrol

What I have tried:

   TabControl tabControl = new TabControl();
       //i have made the tabcontrol  draw mode to be ownerdrawfixed
        private void tabControl_DrawItem(object sender, DrawItemEventArgs e)
        {//this is to color my tabcontrol but nothing happens,it only works if i use drag and drop tabcontrol 
            Brush txt, box_brush;
            Pen bp;
            Rectangle tab_rect = tabControl.GetTabRect(e.Index);
            if (e.State == DrawItemState.Selected)
            {
                e.Graphics.FillRectangle(Brushes.Red, tab_rect);
                e.DrawFocusRectangle();

                txt = Brushes.Black;
                box_brush = Brushes.Silver;
                bp = Pens.DarkBlue;
            }
            else
            {
                e.Graphics.FillRectangle(Brushes.Red, tab_rect);
                txt = Brushes.Blue;
                box_brush = Brushes.Silver;
                bp = Pens.DarkBlue;
            }
        

//BUT I CREATED THE BUTTON UNDER BTNQUESTION
    public void btnquestion_Click(object sender, EventArgs e)
        {
                     
              this.Controls.Add(tabControl);
            int page;
//am= amount of the questions
            int am=20;
             for (int i = 0; i < am; i++)
               {
                  TabPage tp = new TabPage();
                page = i + 1;
                tp.Text = page.ToString();

                tabControl.Controls.Add(tp);
                 
                Label lb1 = new Label();
           RadioButton r1 = new RadioButton(); 
            RadioButton r2 = new RadioButton();
           RadioButton r3 = new RadioButton();
           RadioButton r4 = new RadioButton();
//i have done the locations and the font
                  tp.Controls.Add(lb1);
                    tp.Controls.Add(r1);
                    tp.Controls.Add(r2);
                    tp.Controls.Add(r3);
                    tp.Controls.Add(r4);
        
        }