If you are changing colors more than once, it is best to carry the color not in use loosely along the side of the work. As you carry it up, twist the unused color around the working color every other row as shown to keep the second color in a convenient position. By carrying the yarn, you eliminate the need for sewing in ends later. The second method for changing colors in rib is simply to continue working the initial row of the rib pattern in the new color. It is simply a matter of preference as to which method you choose.
Most basic ribs are elastic by nature.
When laid flat without stretching, the purl stitches tend to disappear to the back, forming a corrugation. Before beginning a garment, decide whether ribbing should be used to pull in the edges or should be stretched and blocked open. With the left-hand needle, lift the last knit stitch over the purl stitch as shown. Knit or purl the next stitch in keeping with the rib pattern.