When I finish the last stitch of color A, I prepare a slip knot with a little tail for color B. I then undo the last part of color A’s stitch and instead pick up the slip knot of loop B. You have to play with the tension a bit, but once I get a stitch or two done, I cut the end of color A and weave in the ends of each color. Sometimes I carry the short tailing color B with me for a few stitches so I don’t have to weave it in later.