winForm中设置Panel的透明度

如题：怎样在winForm中设置我动态添加的Panel的透明度
System.Drawing.Color.FromArgb（）方法只设置了颜色的透明度，而Panel没有透明！private System.Windows.Forms.Panel LoadingPanel = new System.Windows.Forms.Panel();
        public void PanelStart(System.Windows.Forms frm)
        {
            this.LoadingPanel.Location = new System.Drawing.Point(0, 0);
            this.LoadingPanel.Dock = System.Windows.Forms.DockStyle.Fill;
            this.LoadingPanel.Parent = frm;
            this.LoadingPanel.BringToFront();
            this.LoadingPanel.BackColor = System.Drawing.Color.FromArgb(200, 222, 235, 247); 
        }