Casting on 2 Different Colors!

The pattern starts off casting on 17 sts with B and 15 sts with A. How do you avoid the gap in between the two colors or is there a way to join them when casting on?

You want to cross the two yarns the way you would when using two colors for intarsi,a for example (see Free Video, Advanced Techs, Intarsia). In fact, the strands at the cast on won’t stay crossed but you can cross them after you’ve done several rows when you weave in the ends.