use whichever side you like-just rmember if you use the wrong side to consistantly use it that way!:) i once used tone on tone as a background for a scrap quilt that was applique and when i got it all done and was ready to put it on the frame i realized one of the blocks was on the wrong side! oh,well-as my mother would say-you're the only one who knows there's a mistake.i have shown that quilt a qillion times and no one has ever seen the mistake in it.
by the way,many quilter's choose to put a mistake in their quilts.the reasoning is that only god makes things that are perfect....;) just an old quilter.....