Organic agriculture is an ecological production management system that promotes and enhances biodiversity, biological cycles and soil biological activity. It is based on minimal use of off-farm inputs and on management practices that restore, maintain and enhance ecological harmony.
Try using the milk chocolate melts with some black coloring for the black and some white chocolate melts with the yellow and black colorings for the gold (reminder: use the black VERY sparingly).
The latter would still be dark in colour since the cocoa colour overpowers the whiteness of sugar which is the third main ingredient in chocolate. I've both tasted dark-milk chocolates with 75% cocoa content and I've also had dark chocolates with less than 20% cocoa and just sugar for the rest.