EM_SETBKGNDCOLOR Overview Group

The EM_SETBKGNDCOLOR message sets the background color for a rich edit control.

EM_SETBKGNDCOLOR 

wParam = (WPARAM) (BOOL) fUseSysColor; 

lParam = (LPARAM) (COLORREF) clr;

Parameters

fUseSysColor: Value specifying whether to use the system color. If this parameter is nonzero, the background is set to the window background system color. Otherwise, the background is set to the specified color.
clr: COLORREF structure specifying the color if fUseSysColor is zero.

Returns the old background color.