Change picturebox backcolor for x amount of time

Question

I'm trying to change for a preset amount of time the backcolor of a pictureBox when the user clicks a button. I tried to use timers but I saw this Stopwatch on another question. The problem is that the code inside the loop isn't running properly and it keeps crashing.How can I make this work? Code below

private void b_click(object sender, EventArgs e)
{
    Button button = sender as Button;
    Dictionary <Button, PictureBox> buttonDict= new Dictionary<Button, PictureBox>();
    //4 buttons
    buttonDict.Add(bRED, pbRED);
    buttonDict.Add(bBlue, pbBLUE);
    buttonDict.Add(bGREEN, pbGREEN);
    buttonDict.Add(bYELLOW, pbYELLOW);
    Stopwatch s = new Stopwatch();
    s.Start();
    while (s.Elapsed < TimeSpan.FromSeconds(0.5))
    {
        buttonDict[button].BackColor = Color.Black;
        label1.Text = "black";//This part does run
    }
    buttonDict[button].BackColor = Color.White; //the pictureBox does turn white
    s.Stop();
}

Answer 1

Use Timer instead of Stopwatch :

private void b_Click(object sender, EventArgs e)
{
  Button button = sender as Button;
  Dictionary<Button, PictureBox> buttonDict = new Dictionary<Button, PictureBox>();
  //4 buttons
  buttonDict.Add(bRED, pbRED);
  buttonDict.Add(bBlue, pbBLUE);
  buttonDict.Add(bGREEN, pbGREEN);
  buttonDict.Add(bYELLOW, pbYELLOW);
  Timer timer = new Timer();
  timer.Interval = 500;
  timer.Tick += (o, args) =>
  {
    buttonDict[button].BackColor = Color.White;
    timer.Stop();
    timer.Dispose();
  };
  buttonDict[button].BackColor = Color.Black;
  label1.Text = "black";
  timer.Start();
}

Another possibilities, using Task.Run:

private void b_Click(object sender, EventArgs e)
{
  Button button = sender as Button;
  Dictionary<Button, PictureBox> buttonDict = new Dictionary<Button, PictureBox>();
  //4 buttons
  buttonDict.Add(bRED, pbRED);
  buttonDict.Add(bBlue, pbBLUE);
  buttonDict.Add(bGREEN, pbGREEN);
  buttonDict.Add(bYELLOW, pbYELLOW);
  buttonDict[button].BackColor = Color.Black;
  label1.Text = "black";
  Task.Run(() =>
  {
    Thread.Sleep(500);
    Invoke(new MethodInvoker(() =>
    {
      buttonDict[button].BackColor = Color.White;
    }));
  });
}