My method of casting on using two colors and the cable cast-on method is a bit different from what seems the standard two-color cable cast-on. There is a video on YouTube on how I do it.
For short, I make the slipknot in only one color – it is the color I knit first on later rows – and I pick up the yarn for the next stitch from under the other color. The latter makes the yarns twist around each other, so if you intend on casting on more than a dozen stitches, it’s more convenient to pick up one of the colors from over the other color.