Candy Color is oil based, and therefore there is no worry of seizing the chocolate or melted candy coating when tinting. (Water based colors will cause seizing.) We've used Wilton brand as well as Americolor brand with good results.
(via Amazon): Concentrated oil-based color--- Easily blends into Wilton Candy Melts--- Includes Red, Blue, Yellow and Orange--- ¼ oz. Jars