[quote=@Wuldraider]
My personal ideas for the world. Also why do we have to bind so strongly to such a strict idea of magic? Magic is as diverse as people are. On some worlds Red magic might be fire while on others it could be something completely different, for World of Warcraft I know that while fire magic is fire obviously it is also represented as Life magic by the way of the Red Dragonflight. Why can't we have magic of our own kind? I play RW as a bunker til swarm way.
[/quote]

I suggest reading some of Mark Rosewater's articles on the color pie, and I'm sure he has done some articles on the color pairs as well.

The issue with what you said is that fire magic isn't all the red is. Red isn't just flames, it's a rage, passion, emotions, trickery, quick-wittedness, and so much more. The colors of magic are more conceptual than anything, and are extremely flexible. The problem with RW is that its design space hasn't been explored too much beyond "Military" and such. Since it is an enemy color pair, it is a logically conflicted pair. Red is aggressive, white is defensive. White is about working for the greater good, while red is about doing what your heart wants. So, RW is about emotional investment in a cause, working towards something with great zeal. Warriors,  armies, and religious zealots fit into this pair.

I feel like I'm rambling. Basically, RW has always been designed as aggressive, and while defensive RW sounds cool, you'd need to have a solid way of doing it.

About the worldbuilding. Wuld, don't think of it in terms of our characters. Rather, come up with the world wholly seperate from them. Our characters have never been here, and have yet to arrive, what is it like?

About the ally/enemy colors. We can only do one or the other. Given the concept of tri-colored factions with dual-color races, we have to limit ourselves to one, because catering to all 20 possible dual/tri color pairs is impossible in less than 400 cards, and would be similar to just doing mono-color.

If we do ally colors, our factions will be: white-green-blue, white-green-red, black-green-red, black-red-blue, white-blue-black.
Races will be: White-blue, blue-black, black-red, red-green, green-white.

Enemy color facs: white-red-black, white-green-black, white-red-blue, green-blue-black, red-green-blue.
Races: red-white, red-blue, white-black, black-green, green-blue.

[@Marsadept] I don't think there is enough room in a set to cater to both ally and enemy duals.