In the Windows Api and GDI, you can use the default window background color for drawing buttons and stuff (that slight greyish color on Win98 , WinXP + Classic Theme etc. ).
What is the rgb value for that?
So I can emulate the exact color in Allegro using al_map_rgb( r, g, b) ?
It depends on the users settings.
You should use GetSysColor function to retrieve the DWORD value and then use
GetRValue,GetGValue, andGetBValueto retrieve red, green and blue component values.