The common term is blender, not blendables, at least in my part of the country. There was a post on this a couple of weeks ago with some photos that will help you. A blender fabric is used to make a transition between primary focus fabrics. They are usually in similar or complementary colors to the focus fabric but much more subtle in terms of print or hue. Many blenders are small prints in one color with slight variations in the hue or shade of that color so may look almost like a solid but aren't. Batiks are also used as blenders because they can have several colors that tie other fabrics together. A small print can be a blender but blenders don't have to be small prints.