Fade or bleed? If you are talking about bleeding, take a small piece (5 x 5 is what I used). Fold up in a small bowl and pour 1/4-1/3 cup of hot water over it. Let sit a couple of minutes, the remove the fabric. You'll see if it's bled into the water. Another method I read about is to fold a small piece of red and white together. Wet with hot water and see if the white turns pink.
For fading, the only way I can think of is to put a piece in strong sunlight for a time. But it might take several weeks to tell if it will fade.