I thought you were going to use one color. Yes, I think that's how you do it, I've only done a single color. The CO instructions for the heart hot pad which uses 2 colors read:
" I like a two color cast on. You can do a Long-Tail Cast-on with both strands of yarn worked as if they were one strand. Then work each strand as its own stitch on the first row. If you Cast on this way, then Cast-on 30 of these double stitches, to end up with 60 workable stitches. Or you can use a single backward loop cast-on in one color; which is what is pictured in the photo, and demonstrated in the project video on the KnittingHelp CD. Cast-on 60 stitches in this case."