Knitting stripes is the easiest way for knitters to add their own touch to a project and to add a bit of color to what would otherwise be a plain knit fabric.
Some new knitters are mystified by how to join a new ball of yarn and begin knitting in a new color to knit stripes, but it's really quite easy to do so.
To begin, cast on and knit (or work whatever pattern stitch you like) as many rows as you would like for the first color of yarn you're using.
It's a good idea to change colors on right-side rows, particularly in stitch patterns like Garter and Stockinette. This will make the color change crisp and straight rather than dotted.