procedure TForm1.Button1Click(Sender: TObject);
var
 Bm1: TBitmap;
 Bm2: TBitmap;
begin
 Bm1 := TBitmap.Create;
 Bm2 := TBitmap.Create;
 Bm1.LoadFromFile('c:\download\test.bmp');
 Bm2.Width := Bm1.Width;
 Bm2.Height := Bm1.Height;
 bm2.Canvas.Brush.Color := CoolBar1.Color;
 bm2.Canvas.BrushCopy(Rect(0, 0, bm2.Width, bm2.Height), Bm1,
  Rect(0, 0, Bm1.width, Bm1.Height), ClWhite);
 bm1.Free;
 CoolBar1.Bitmap.Assign(bm2);
 bm2.Free;
end;