Set up: Tie the ends of the two colors together. Hold the two colors by the knot so that the contrast color is towards you. Put the tips of your left thumb and forefinger together and poke your thumb and forefinger between the two colors about 6″ below the knot. Grab the tails of both colors with your other three left fingers and spread your thumb and forefinger into a “U”. Now bring the knot end down between your thumb and forefinger and hold it with the needle in your right hand.
Step 1: Put the needle into the loop on your thumb (CC) as you would for the long-tail cast on, go over the first yarn on your forefinger (MC), scooping that yarn and the needle back into and through the loop on the thumb – moving out towards the thumb pad and wrist. Once the needle has cleared the loop, slide your thumb from the loop. Put your thumb back between the two colors (the MC remains on your forefinger) and use the thumb to tighten the loop on the needle. Bring your thumb and forefinger up into the “U” position.
Rep Step 1 for the required number of stitches. After the second cast on stitch, you can drop the knotted yarn from your right hand.
See also: 2-color k/p flexible long-tail cast on, Long Tail Cast On, e-wrap or backwards loop cast on