If the fabric is going to be the "main' fabric, then three yards, everything else 2 yards except backs. If a back is going to be 45" wide, then I buy the length x 2, or five yards. Better yet, buy a 108 to 110 inch fabric, then you just have to buy the smaller length. While the cost of a yard is more, I need less yards, so the price is cheaper. Example: $15/yd x 2 yards = $30 instead of $6/yd x 5 yards = $35.
BTW I think of a Blender as something that will tie together two different patterns or colors together. So a blender could be a pink and yellow batik that "blends" a pink pattern with a yellow pattern together in the same quilt.