If you're talking about the Wilton aerosol colors, I've used them and they're great for both fondant and buttercream and they leave no discernible taste (one of the few Wilton products I endorse wholeheartedly, except for the limited range of colors they come in). If you're talking about airbrushing, that's even better, especially when you need a deep, rich, saturated color. I have one that I've been too chicken to use yet, but I just got an instructional video, so I'll be trying it out shortly!
I've used the Wilton spray colors and they work great for what I've needed them for. A light mist and no taste. But, I'm not sure I would trust them to completely cover a MMF cake in black.
Hi, klamb17!! This is my experience with specifically the black Wilton spray: On May of last year I made a Michael Jackson cake for my son, and since I was not looking forward to tint the MMF to black I decided to use the Wilton spray and to make sure I had enough color I bought 3 canisters of black. You can look at the cake in my gallery, it never turned black 
I was panicking but the cake was saved because I remember I had black sugar, which I use to cover the 10in cake .
You can still see the gray under the black sugar, my son did not notice!! 
He loved his cake (he still is a Michael Jackson fan)
Now if you can get your hands on an airspray machine that would be awesome!!!
http://cakecentral.com/gallery/2041616/this-is-it
God luck! 
CIAO
When I need to use black fondant I will tint it as dark as I can, then spray the fondant after it's on the cake with the black. Then you don't have to use to much of either and its worked for me. I also have an airbrush but have been to afraid to try it but I have used several of the spray colors with no problems.
I use sprays for gold, silver, & white pearl.
For black fondant, I buy it (red, too). I love, love, love, Duff's black fondant and I also use Satin Ice & FondX.
Rae
I've never used it on fondant, but I have used it on buttercream. I think it would take too much to get a good solid color and I personally think you can taste it if you use a lot. Plus you'd have to worry about it running if you don't allow it to dry completely between layers. I personally would just get a black fondant.
Worry about your problem with black spray, soledad, but the cake turned out awesome! I've used the black soray with no problem with a stencil on a cake that's not in my gallery (I could never download it from my ancient cell phone!). But I have to say that when I really need black or red, I use Satin Ice, which is really rich in color and doesn't taste too bad (a little chemical-y, but not gross).
and thank you I appreciate your comment!Quote by @%username% on %date%
%body%