procedure TForm .Button Click(Sender: TObject);

var
  Bm  : TBitmap;
  Bm2 : TBitmap;
begin
  Bm  := TBitmap.Create;
  Bm2 := TBitmap.Create;
  Bm .LoadFromFile('c:\download\test.bmp');
  Bm2.Width := Bm .Width;
  Bm2.Height := Bm .Height;
  bm2.Canvas.Brush.Color := CoolBar .Color;
  bm2.Canvas.BrushCopy(Rect(0, 0, bm2.Width, bm2.Height),
                       Bm ,
                       Rect(0, 0, Bm .width, Bm .Height),
                       ClWhite);
  bm .Free;
  CoolBar .Bitmap.Assign(bm2);
  bm2.Free;
end;