I tend to let the quilt dictate the width of the binding, but, usually I make mine 2 1/2". Since I do not make quilts to enter in shows or as heirloom (although I would like to think they are treasures!), I prefer to machine stitch my binding instead of hand sewing. I know there are many out there gasping at the thought! I attach the binding to the back, bring it around to the front and then use a decorative stitch to attach it. My favorite is a stitch that is wavy with a little leaf on it. This not only looks pretty, but if the stitch 'wanders' on the back a bit, it looks intentional. As far as the color, again, your top should let you know what it needs. Does it want something to blend in? or frame? I just finished a kaleidoscope with lots of white and the border needed something. I took all the scraps of color and creating a binding - perfect touch at the edge. Another favorite is a tiny stripe cut on the bias - makes an interesting but subtle edging. Even big prints cut in strips can be very nice. Remember - your quilt - your rules!