Prevent CellForeColor and CellBackColor from being set to the same values (Conditional Formatting)

this.radGridView1.ConditionalFormattingFormShown += RadGridView1_ConditionalFormattingFormShown;

private void RadGridView1_ConditionalFormattingFormShown(object sender, EventArgs e)
{
    var conditionalFormattingForm = sender as ConditionalFormattingForm;
    var propertyGrid = conditionalFormattingForm.Controls[0] as RadPropertyGrid;
    propertyGrid.PropertyValueChanging -= PropertyGrid_PropertyValueChanging;
    propertyGrid.PropertyValueChanging += PropertyGrid_PropertyValueChanging;
}

private void PropertyGrid_PropertyValueChanging(object sender, PropertyGridItemValueChangingEventArgs e)
{
    var proertyGridTableElement = sender as PropertyGridTableElement;
    var propertyGridItem = e.Item;
    var propertyGridElement = e.PropertyGridElement;
    if (e.Item.Name == "CellForeColor" )
    {
        var newColor = e.NewValue;
        if(propertyGridElement.PropertyItems.FirstOrDefault(x=>x.Name == "CellBackColor").Value.ToString() == newColor.ToString())
        {
            e.Cancel = true;
            MessageBox.Show("CellForeColor and CellBackColor properties have the same colors!");
        }
    }
    else if(e.Item.Name == "CellBackColor")
    {
        var newColor = e.NewValue;
        if (propertyGridElement.PropertyItems.FirstOrDefault(x => x.Name == "CellForeColor").Value.ToString() == newColor.ToString())
        {
            e.Cancel = true;
            MessageBox.Show("CellForeColor and CellBackColor properties have the same colors!");
        }
    }
}