WM_PALETTEISCHANGING
hwndRealize = (HWND) wParam; /* handle of window to realize palette */
The WM_PALETTEISCHANGING message informs applications that an application is going to realize its logical palette.
hwndRealize
Value of wParam. Specifies the handle of the window that is going to realize its logical palette.
An application should return zero if it processes this message.