Coloring a white chocolate drip is super easy!  The easiest way is to use colored candy melts in place of the white, such as pink candy melts for a pink drip, blue candy melts for a blue drip, etc.   But, you can also mix in gel food coloring to the melted ganache to get your desired color. The white chocolate ganache tends to have a yellow hue so it can help to use white food coloring first, then add your desired gel food coloring for a brighter more true color.