I'm one of those folks who likes to try and do as much in advance as possible.  I'd like to go ahead and color some fondant in advance and just keep it in a ziploc bag for when I'm ready to use it.  Does anyone know how far in advance I can do this and how long the color will stay before fading?  

TIA

I use MMF.  The color will not fade.  As it sits it will get darker.  I have mine in the refrigerator and take it out and let it sit to get it to room temperature, knead and use it.  I have had fondant for several months in the refrigerator with no problem when I am ready to use it.  I also make my fondant at least 2 weeks in advance of when I need it.

I don't have any issues with any color except with purple.   Just keep it out of the light as much as possible! I made a rainbow that needed to dry and just kept a paper towel over it and the colors were all vibrant - I had to dust the purple but the rest were perfect!