I have to make a peacock cake so i am looking forward to make metallic colored fondant and buttercream. I have AmeriColor Amerimist Student Kit Air Brush Food Color 12 Pack Kit can i mix the directly in to fondant or buttercream??? Can any one reply ASAP...  :(

Airbrush colors can be used to tint fondant/icing, but they are MUCH higher in moisture/water and will make the fondant/icing sticky if you need a high level of pigment density.

And know that you will NOT make "metallic" fondant/icing by mixing in metallic colors. The fondant/icing will coat the metallic particles and greatly dull their glitteryness. 

If you have to have a metallic finish and do not have an airbrush for your metallic colors - test using a paint brush. But, you will NOT get as smooth a finish as with a properly applied airbrush.

I´ve done it with BC and it works fine. I haven't ever tried with fondant. Airbrush colour is fairly liquid but highly concentrated. I would test on a small ball of fondant first to see if you get the colour you need without making the fondant too sticky to work with. 

Oops sorry, didn´t read the metallic bit. I don't think metallics work, so look to applying the metallic colour later, with an airbrush or paintbrush. There are numerous threads on CC about adding luster dust and things to BC and fondant and the outcome is never much good. 

I have a bit of experience with fondant and buttercream. I know that you can mix the air brush food coloring into fondant but it may be a big mess at first, however, if you use the Americolor gel color, it should work a lot better. I get mine on Ultimate Bakers site http://www.cooksdream.com/store/category/color75.html 

You can def mix the air brush color into the buttercream. :) Hope your cake turns out well.