[Alegun]

Похоже проще "мышиной" ловушкой

Код:

var
 MouseHook: HHOOK;
function LowLevelMouseProc(nCode: Integer; WParam: WPARAM; LParam: LPARAM): LRESULT; stdcall;
var
 DC: HDC;
 Cur: TPoint;
begin
 Result:= CallNextHookEx(MouseHook, nCode, WParam, LParam);

 if WParam = WM_MBUTTONDOWN then
  begin
   DC:= CreateDC('MONITOR', nil, nil, nil);
   Windows.GetCursorPos(Cur);
   Form1.Label8.Color:= GetPixel(DC, Cur.X, Cur.Y);
   DeleteDC(DC);
  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
 MouseHook:= SetWindowsHookEx(14 {для клавиатуры 13}, @LowLevelMouseProc, HInstance, 0);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
 UnhookWindowsHookEx(MouseHook);
end;