I really respect what your teacher said about the refrigeration issue... but I have always put mine in the refrigerator (both royal and color flow) and I never had a problem with them.
Good tips for storing are: put your icing in an air tight container and cover it with a piece of plastic wrap to avoid crusting.
Every single time you use it, you have to stir it to get rid of that "spongy" look and the only thing you have to be careful is to clean all your utensils and tips, because if there is a little bit of shortening or butter on them, your royal or color flow is going to get ruined.
I just realized something... are you talking about a finish color flow piece???
In that case..... just let it dry anywhere. I let mine dry for 2-3 days and then put them in a little box. I keep the little crisco plastic boxes to store all my royal flowers and small color flow pieces. 
I have not made mine yet but my instructor told us to cover it with plastic wrap and then seal it in an airtight container until class. I have class Tuesday and am going to wait to make it until right before class. Good Luck!
The only things that need to be in the fridge are those that contain eggs, milk, and maybe butter. Once I learned this I always use water to make everything. (I live with my husband at a Seminary where he's a student. I literally have a fridge the size of a small hotel room kitchen!!!) I use disposable tubs and write the date and recipe on the outside with a sharpie (bc, royal, etc.) as well as the consistency (thin, thick, etc.). Take enough classes like me and you'll use stuff up quickly! I don't remember color flow having anything of danger in it. I never keep mine in the fridge. One note I learned: be sure to pop any air bubbles with a pin as soon as they develop, not after it's hard!
Blessings!
Use a glass container with plastic wrap covering the top of the color flow then another piece over the top of the glass container. You can store it in the refrigerator until needed. I say glass because you can tell if there is any grease on it. That's one thing you don't want to have on your tips-bags-or bowl.
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