procedure TformMain.ButtonDoReplaceColorClick(Sender: TObject);
begin
  ImageEnViewPixelEditor.Proc.CastColorRange(
  TColor2TRGB(PanelReplaceColorsPickedColor.Color), // OldColor
  TColor2TRGB(PanelReplacementColor.Color),         // NewColor
  TrackBarColorReplacementTolerance.Position);      // Tolerance
end;

if ImageEnView1.Selected then // if a selection exists
begin
  var ThisIEBitmap: TIEBitmap;
  // Create the TIEBitmap to hold the selection:
  ThisIEBitmap := TIEBitmap.Create;
  try
    // Copy the selection to the ThisIEBitmap:
    ImageEnView1.CopySelectionToIEBitmap(ThisIEBitmap);
    // Copy the ThisIEBitmap to another ImageEnView:
    ImageEnViewDummy.IEBitmap.Assign(ThisIEBitmap);
  finally
    ThisIEBitmap.Free;
  end;
  // Replace the color in the other ImageEnView:
  ImageEnViewDummy.Proc.CastColorRange(
    TColor2TRGB(PanelReplaceColorsPickedColor.Color), // OldColor
    TColor2TRGB(PanelReplacementColor.Color),         // NewColor
    cxTrackBarColorReplacementTolerance.Position);    // Tolerance
  // Copy the IEBitmap from the other ImageEnView to the selection in the main ImageEnview:
  ImageEnView1.ApplyBitmapToSelection(ImageEnViewDummy.IEBitmap);
end;

// Create the TIEBitmap to hold the selection:
var ThisIEBitmap := TIEBitmap.Create;
try
  // Copy the selection to the ThisIEBitmap:
  ImageEnView1.CopySelectionToIEBitmap(ThisIEBitmap);

  var proc := TImageEnProc.CreateFromBitmap(ThisIEBitmap);
  try
    proc.CastColorRange(
      TColor2TRGB(PanelReplaceColorsPickedColor.Color), // OldColor
      TColor2TRGB(PanelReplacementColor.Color),         // NewColor
      cxTrackBarColorReplacementTolerance.Position);    // Tolerance

    // Copy the ThisIEBitmap to the main ImageEnView:
    ImageEnView1.ApplyBitmapToSelection(ThisIEBitmap);
  finally
    proc.Free;
  end;
finally
  ThisIEBitmap.Free;
end;