I will try to answer, although I have win7.
In the image below you have a typical one SplitContainer. It consists of:
- Return Line Color SplitContainer;
- Panel 1 backcolor
- Panel 2 backcolor
- parent container backcolor

, , . . .
, . -. - . , - Padding ( 0;0;0;0), Margin ( 0;0;0;0), , , , , , , - ( ) - , - .
( , ) : splitcontainer, panel1, panel2 ( , ). . , , .