Follow three steps process to set the transparent color.
Step 1: Locate the constructor for your control class.
Step 2: In the constructor, call the SetStyle method of your form. This will enable your control to support a transparent backcolor.
SetStyle(ControlStyles.SupportsTransparentBackColor, true);
Step 3: After the line of code you added in the previous step, set your control's BackColor to Transparent.
this.BackColor = Color.Transparent;