With CA, ch 152.
Row 1 (Wrong Side): Sc in 2nd ch from hook and in each ch across; turn - 151 sc.
Row 2 (Right Side): Ch 1, sc in first sc, * skip next 4 sc; 9 dtr in next sc - shell made; skip next 4 sc; sc in next sc; rep from * across, changing to CB in last sc; turn.
Row 3: With CB, ch 5 (counts as a tr and ch-1 sp), 2 tr in first sc, * ch 2, skip 4 dtr, sc in next dtr, ch 2, skip 4 dtr **, (2 tr, ch 1, 2 tr) all in next sc; rep from * to last sc, end at **; (2 tr, ch 1, tr) all in last sc; turn.
Row 4: Ch 5 (counts as dtr), 4 dtr in ch-1 sp, sc in next sc, * shell in next ch-1 sp, sc in next sc; rep from * to last sp; 4 dtr in ch-1 sp, dtr in 4th ch of ch-5 changing to CC; turn.
Row 5: With CC, ch 1, sc in first dtr, * ch 2, skip 4 dtr, (2 tr, ch 1, 2 tr) all in next sc, ch 2, skip 4 dtr, sc in next dtr; rep from * across working last sc in top of ch-5; turn.
Row 6: Ch 1, sc in first sc, * shell in next ch-1 sp, sc in next sc; rep from * across changing to CA in last sc; turn.

Rep Rows 3-6 for pattern, working color sequence of [2 rows CA, 2 rows CB, 2 rows CC] 12 times, then 1 more row CA (wrong side); now turn and work Edging around all edges: With CA, ch 1, sc evenly around, increasing at corners to keep work flat; join to first sc. Fasten off. With right side facing, attach CB and work 1 rnd sc, increasing at corners as before; join. Fasten off. Rep last rnd with CC, then again with CA. Weave in ends.