My binding is always 2 1/2 inches cut and then I fold it in half. Soooo to make a two color binding I cut the strip that is going to be on top 1 inch and the strip that will show on the back two inch then sew them together. the strip should measure a 2 1/2 inch. Then fold that in half and you are ready to put it on your quilt. I made a sample and have it on my work station board to refer to when I need it. Also if I run short on fabric and have a 2 inch strip to begin with I sew another piece on it and fold it in half and hide the piece in the binding. No one will ever see it. I hope all this is clearer than mud Marge