When the pattern has horizontal stripes
Knitting - Basic Techniques

For a narrow stripe pattern (2 to 6 rows), carry the yarn not in use loosely up the side of the piece; each time the color changes, bring it up and continue without cutting the yarn.

	Drop color B, bring color A up to the beginning of the next row. With color A in front of color B (always keep the new yarn for the next stripe in front), knit.