Can royal icing be painted after it dries? Will it fall apart again?
Yes, it can be painted. Use a mix of gel color paste and a clear alcohol such as vodka. Go easy, don't be heavy-handed with the paint. It's better to do several coats than to over-load it or it could melt.
besides painting on it, you can also use the Food Writers on royal icing. Plus I have used my airbrush to color things I have done with royal icing and have even used the aerosol colors at times when I didn' want to get the airbrush out.
Just make sure that the royal icing i really dry and everything should be fine. Have fun and let us see photos of what you are doing.
I painted pansies with water and paste food color and they did not disolve it does not take much liquid when you paint.