Q: How to get color depth?
A: use the following:

function GetDisplayBPP: Integer;
var
  DC: HDC;
begin
  DC := GetDC(0);
  Result := GetDeviceCaps(DC, BITSPIXEL) * GetDeviceCaps(DC, PLANES);
  ReleaseDC (0, DC);
end;

    Source: geocities.com/huanlin_tsai/faq

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