I have sprayed color mist once in the past on some dried gumpaste and it only lasted a day or so. Is this normal? I am trying to assemble my first big bow for a Christmas cake and was wondering if I should bother spraying before or after. I could just spray the day of and not worry huh?
Sorry I have no advice really for you. I used it once recently on some whipped frosting and it worked nicely.
I did test a couple days before on some RI cookies, plain cookies, and whipped frosting and had no fading on what I left to dry (ate the other ones!).
I can only suggest spraying early the same day you intend on showing/using the pieces so they dry but the color is still strong.
If you are in doubt I would wait as long as possible before spraying the bow. I have used the colormist a few times and it did fine making the cake two days ahead.
I think what would work the best would be airbrush...something I hope to get in the near future! 
Quote by @%username% on %date%
%body%