If you want to know what some of the ingredients for the cakes are or where they are bought, then this is the place with the answers.

Icing colors:
Icing colors is very concentrated color for food. It has no taste and the color is so concentrated that you only have to use a few drops at the time. Personally I just toothpicks to take small drops with.
I use some made by Wilton, because in my experience they are the best ones. They can be bought in a huge variety of color and can be mixed.

Spray for cakes:
Can be bought in gold & silver (and perhaps also in other colors) and it’s edible. Cover around the cake and open a window when you spray. Let the cake rest for a while and it’s ready. The gold spray I used is made by Wilton.