private Color?[] _colors = new Color?[] { null, Colors.AliceBlue, Colors.AntiqueWhite, Colors.Azure, Colors.Beige, Colors.Bisque, Colors.BlanchedAlmond, Colors.BurlyWood, Colors.Cornsilk, Colors.LightGoldenrodYellow, Colors.Linen, Colors.MistyRose, Colors.Moccasin, Colors.PapayaWhip, Colors.SeaShell, Colors.Black };
private void OnColumnOptionsLoading(object sender, GridColumnOptionsLoadingEventArgs e)
{
    if (e.Menu.Items.Count > 0)
        e.Menu.Items.Add(new C1MenuSeparator());
    var menuItem = new C1MenuItem();
    menuItem.Header = "Column background";
    menuItem.Icon = new Border { BorderThickness = new Thickness(1), BorderBrush = new SolidColorBrush(Colors.Black), Background = e.Column.Background };
    foreach (var color in _colors)
    {
        var colorMenuItem = new C1MenuItem();
        colorMenuItem.Tag = color;
        colorMenuItem.Header = color?.ToString() ?? "None";
        colorMenuItem.Icon = new Border { BorderThickness = new Thickness(1), BorderBrush = new SolidColorBrush(Colors.Black), Background = color.HasValue ? new SolidColorBrush(color.Value) : null };
        colorMenuItem.Click += (s, oe) =>
        {
            var color = (Color?)(s as C1MenuItem).Tag;
            e.Column.Background = color.HasValue ? new SolidColorBrush(color.Value) : null;
            e.Close(); //This closes the menu.
        };
        menuItem.Items.Add(colorMenuItem);
    }
}