First off, I would also pay extra for colored carts.  The only ones I can find for 510's is black.  I would like colors just to have them - not just for sorting.  I know, I am such a girl.  Secondly, I just reorganized my carts and rubberbanded them to the flavor, but that ammo thing is cool.  I am such a sucker when it comes to buying new stuff.
My flavors are all just lined up on a counter.  I do not have children around and my animals can't get to them.  But, should they be in another type of container?  Does keeping them in a closed container keep the flavor better?