I guess it depends how long you want to store it. I've stored it in a ziploc baggie on my counter for a few days... then just microwaved it a few seconds when I needed it again. I've heard some ppl say they have kept in the fride and microwaved it too...depending on the humidity level in your fridge...
I just double wrap it in plastic wrap and put in a ziplock on the counter.
Thanks for the help. I used the MMF recipe here on CC I didnt realize how much it makes . And I just have to comment on the Americolor Gel paste I received my order the other day and I just used the Violet and wow it just takes very little I am so impressed with it . I love it. This is the greatest site on the net.
cashley....was that in your fridge or on the counter?
I wrap in plastic wrap and put it in a gallon ziplock. Caution - it will become very hard, like a rock, but that's ok - just pull or cut some off when you need it, put it in a greased bowl in the microwave for 5 - 10 seconds, knead it, and it's perfect! 
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