We made about 175 3D cookies for the staff at work. I made the Royal Icing, and it was very easy to work with. We used zip lock bags and cut a very small piece of one end off. For the coloring, I used Wilton's concentrated paste, and the colors are great. While the icing was still wet, we added sprinkles to some, gold and silver balls to others etc. It hardened very well, and they are still intact! Good luck and have fun.
Here's the recipe I use for Royal Icing
1 egg white
1 3/4 cups powdered sugar
1 tsp water
food colouring optional
Combine egg white and powdered sugar. Beat on low speed until well blended. Add water and blend well. If too thick add water drop by drop. If too thin, add a bit of icing sugar at a time. Add the food colouring once the icing has reached the disired consistency.
Practice safe lunch. Use a condiment.