Comparing string to background color

private void Button_Click(object sender, RoutedEventArgs e){
    Button btn = (Button)sender;
    if(/*insert if condition here*/)
    {
        cntr = 1;
        void1();
    }
}

I'm currently developing a C# Windows store app. I have a TextBlock that can have a text of either Red, Orange, Yellow, Green, Blue, Indigo or Violet. I also have seven buttons with different background colors. Now, I want to check if the text of my TextBlock matches the backgound color of the Button clicked.