I have notice at some shops that i have visit in the past that the dummy cakes in their showroom look dull. Is there anything that can be done to keep the vibrant colors on the dummy cakes???
Other than keeping them out of the sun I don't know of anything.
Use acrylic paint in the icing instead of food coloring. Some colors will still fade but they usually hold up better.
You can also coat them with crisco every so often to revive them a little when they start to look dull, but this all depends on the decorations on them.
For dummy cakes I use spray paints or acrylics. If I use acrylic, I spray it down with a clear, matte finish spray so it's not all shiny and "fake" looking.
Purple is the absolute worst about this. Definitely keep it out of the sun.
Bright lite will fade some colors.... that is just what happens.