uses
  Windows, Vcl.Dialogs, Vcl.Forms, System.SysUtils, Classes, Data.DBXFirebird, uni, Vcl.controls, imageenIO, ieview, imageenview, ievect, imageenproc,
  WinApi.WinSvc;
. . .
myIO := TImageEnIO.Create(nil);
   try
      myIO.LoadFromFileBMP(FileName);
      myIO.Update;
      myIO.Params.GIF_FlagTranspColor := True;
      myIO.Params.GIF_TranspColor := CreateRGB(255, 255, 255); <-- Error
      myIO.SaveToFileGIF(NewFileName);
      Result := true;
   finally
     myIO.Free;
     myIO := nil;
   end;