This is the Chocolate Ingredient series.
Ingredient Part 1
Milk chocolate's ingredients are cocoa liquor, cocoa butter, sugar, milk or cream powder and spices. The chocolate must contain at least 10% cocoa liquor.
Milk chocolate flavor has a lot to do with the type of milk or cream product that is used by its manufacturer as well as the strength and taste of the cocoa liquor. Because the added milk or cream softens or masks the flavor of the chocolate liquor, most manufacturers rely on the forastero beans to deliver flavor - thinking that their consumers won't know the difference. When you taste a beautifully made milk chocolate containing a fine quality cocoa liquor next to a supermarket milk chocolate bar - the difference will amaze you.
Here is an article about French white chocolate.
Dark milk chocolate - there is a trend by artisan chocolatiers to use a "dark" milk chocolate which contains a higher percentage of cocoa liquor. This gives the creamy milk chocolate a more pronounced flavor.
White chocolate: Because there is so little "chocolate" in white chocolate, the different products available seem to all taste the same. The flavor is mainly one of milk, vanilla and sugar. Is white chocolate actually contain chocolate? Yes, it must contain at least 20% cocoa butter. It may also contain sugar, milk or cream powder and spices. All the lovely phenolic flavours of chocolate are from cocoa solids.
Note: picture is not mine. It is from here.