With B, cast on 67 sts.
Work in St st (k on RS, p on WS) in stripe sequence as follows:
*Work 16 rows with B, 18 rows with A, 12 rows with C, 8 rows with B, 10 rows with A, 6 rows with C, 10 rows with B, 6 rows with C; rep from * for stripe sequence.
Work 86 row stripe sequence for a total of 4 times.
Bind off, leaving a long yarn tail.
Thread yarn tail into blunt needle and seam ends of piece to make a tube. Weave in ends.