I'm not sure why but when I tried violet food coloring it became a gray blue color. Even when I tried to use red and blue coloring I got the same result. Does anyone have any solutions? I have a graduation cake that I need it for.
Purple is hard to get and is not a very stable color, it will fade easily.
it takes a lot of color, so you probably have to add some softed powdered sugar and/or cornstarch to make up for the added moisture.
then, it must be protected from the light. You can help by brushing color dust on the exterior.