const 
  LAYERED = 524288; 
 
procedure Transparenz(h: THandle; Farbe: TColor); 
var 
  m: Thandle; 
  f: function(hwnd: HWND; crKey: DWord; bAlpha: Byte; 
    dwFlags: Longint): Longint; stdcall; 
begin 
  m := LoadLibrary('User32.dll'); 
  if m <> 0 then begin 
    @f := GetProcAddress(m, 'SetLayeredWindowAttributes'); 
    if @f <> nil then begin 
      SetWindowLong(h, GWL_EXSTYLE, GetWindowLong(h, GWL_EXSTYLE) or LAYERED); 
      f(h, ColorToRGB(Farbe), 0, 1); 
      freelibrary(m); 
    end; 
  end; 
end; 
 
procedure Normal(h: THandle); 
begin 
  SetWindowLong(h, GWL_EXSTYLE, GetWindowLong(h, GWL_EXSTYLE) 
    and not LAYERED); 
end; 
 
// Tranzparenz einstellen 
procedure TForm1.SpeedButton1Click(Sender: TObject); 
begin 
  Transparenz(handle, color); 
end; 
 
// Tranzparenz abschaltehn 
procedure TForm1.SpeedButton2Click(Sender: TObject); 
begin 
  Normal(handle); 
end;