Rainbow Stripe Pattern in Feather and Fan Knit Stitch.

Color A, cast on a multiple of 18 sts.
Row 1 - RS: Color A, knit.
Row 2: Color A, knit.
Row 3: Color B, knit.
Row 4: Color B, purl.
Row 5: Color B, * (k2tog) 3 times, (yo, k1) 6 times, (k2tog) 3 times; rep from * to end.
Row 6: Color B, purl.
You can change the color B to any color you like. Repeat Rows 1 - 6.

Knitting abbreviations:
K: Knit | P: Purl | Yo: Yarn over | K2tog: Knit 2 sts together.