Change background and font color of GridView (Windows 10 App)

I have a GridView with several numbers and I have a click event on the items in this GridView. I would like the items that were already clicked to change the colors of the background and the text, to indicate to the user that they have already clicked on them.

The event is this:

private void dataGridNumbers_Tapped(object sender, TappedRoutedEventArgs e)
{
    string selectedNumber = dataGridNumbers.SelectedItem.ToString();

    if (selectedNumber == resposta)
    {
        txtBoxInfo.Text = "Congratulations! You Find the Ramdon Number!";
    }
    if (selectedNumber != resposta)
    {
        numbersCloser(Int32.Parse(selectedNumber));
    }
}