What are the ingredients inside of white chocolate that makes it melt faster than dark and milk cho.

I am doing a project on which chocolate melts faster and I need to know the ingredients inside of the white chocolate..and the dark chocolate..and the milk chocolate. That makes it melt faster inside of a microwave.

You can look on the package to see the ingredients. Could it have anything to do with light colors reflecting heat and dark colors absorbing it? That's not a hint. I don't know the answer but your question made me wonder if that could be a factor.