I don't know what Colinda used, but I've used the colored candy melts you can get at craft stores to good effect in the past. I'd worry that food coloring would change the texture of white chocolate too much.
Yep, I used colored candy melts. For the yellow "stars" on the Christmas trees, I used yellow food dye in the white chocolate and it did mess up the texture, but since it was just a dot on a few of them, I didn't really worry about it. So I melted the green & red candy melts, used a toothpick to poke a hole in the corner of a Ziploc bag, and piped my designs on that way. Can you find colored candy melts down there? Or can your mom or someone send you some?
Re: Colinda