I recently wanted to dye some frosting and decided to do a little experimenting!
I used ground tumeric to tint my frosting yellow. I sprinkled about a quarter of a teaspoon of tumeric over 8oz. cream cheese and 4oz. butter and beat until smooth and light. I waited about 30 minutes for the color to absorb and then I mixed in enough powdered sugar to make a nice frosting, about 1 lb.
I put the frosting into a container and refrigerated it overnight. The yellow color became brighter and deeper the longer it sat. I could taste the tumeric a little bit, but I was still very happy with how well the frosting turned out.
The next color I decided to try was red.
I drained all of the liquid out of a jar of beets.
I boiled the liquid in a sauce pan on the stove until in reduced to a thick syrup. Then I cooled the syrup by putting the sauce pan into a sink of cold water.
When the beet syrup was cooled I added it to a small amount of frosting. It did not dye the frosting red, but it did make a pleasant Rose color.
Here is a cake I decorated with the colored frosting.
The yellow is little brighter than what is showing up in the picture.
I just used melted baker's chocolate for the eyes and outlines.