Row 1: With color 1, foundation sc 100 (I prefer using foundation stitch rather than chains.)
Row 2: Ch3, turn, 2dc in first fsc, (sk2, sc-2dc in next st), rep () across, sc in last st.
Row 3-4: Ch2, turn, 2dc in first sc, (sk2, sc-2dc in next st), rep () across, sc in top of ch2.
Row 5-6: Change to color 2, rep row 3.
Row 7-9: Change to color 1, rep row 3.
Row 10-69: Rep rows 5-6 and 7-9.
Row 70: Still in color 1, ch1, turn, hdc in first st, (sc in next 2 dcs, hdc in next sc), rep () across ending with sc in beg hdc.
Border: Still in color 1, ch1, crochet evenly around with 3sc in ea corner. Ch1, turn, crochet around, with 3sc in ea corner. Rep last row. Fasten off and weave in ends.