Place your cornstarch in a small to medium bowl. Add the water a teaspoon or two at a time. When you reach about halfway through the 1/2 of the 1/4 cup of water, stir in the honey. Then add the remaining water until you reach your desired consistency. This will normally seem a bit thin at first before it actually hardens
Divide the icing into as many bowls as you want colors. For example, if you want two colors, divide the icing into two smaller bowls. Then add a drop or more of the food coloring to the individual bowl and mix until you get your desired color for icing.
As mentioned, we will be using corn starch for this recipe. Cornstarch is a thickener that helps this harden.
There are a few alternatives to cornstarch that can be subbed in for a recipe such as this one.
Rice flour or potato flour should work although you may need to add a bit extra for hardening. Tapioca Starch and Arrowroot Starch are two other possible alternatives for you to try as well.