I can't remember which site I saw it on, but one article I read stated you can switch colors throughout the day. For instance, if you start with a blue tag but want to park in a red area, they'll give you a red tag at that parking area.
I still don't really understand the point of this. I imagine there will still be tons of people who park their stroller wherever, CMs still moving strollers within sections as people reclaim their stroller, and people still having trouble finding their stroller. I see it being a pain for people having to make sure they are in the right section or find the CM (or check in with them just to park the stroller) to get a new tag, then remembering how to get to where their designated section after the ride. It won't be as simple as "oh look, there's a bunch of strollers- let's park there," or "That's where we must have left it, because that's where I see a bunch of strollers."
I would like to think that Disney has some sort of method to their madness on this one, but I can't quite figure out what it is.