Lidia - from chicago, IL
I think the addition of milk and food coloring caused your white chocolate to seize. This happens when an improper amount of moisture comes into contact with chocolate. For molding candies, you don't want to add any liquid to melted chocolate. The chocolate should be melted on it's own. White chocolate can be colored with oil-based food colorings, like Wilton's Candy Colors, but not with water-based food colors, which are much more common. Water-based colors will add moisture to the chocolate and make it seize up.