Add more two rows to the ripple pattern to create clear gap at colour change and the ridge.

Ripple patterns
Row 1 : Knit all
Row 2 : Purl all
Row 3 : (K2tog)twice, (yo,K1) 4times, (K2tog)twice to end
Row 4 : Knit all

Repeat above till row 12

Row 13 : Knit all
Row 14 : Purl all

Patterns works as ;

1. Cast on 162 sts and work in garter st 6 rows.
2. (3 ridges) 13 X Ripple Pattern (3 ridges)
3. 4 row garter sts

repeat 2 X 17 times (white)
repeat 3 X 16 times (colours)

finished up with garter st 6 rows.