Each card in the cycle of five Weavers, reprinted from Invasion, gives benefits to its color's allies. The demonstration of the colors' enemy relationships is a bit more subtle, but is present in the form of Coldsnap's "color hosers": Luminesce, Flashfreeze, Deathmark, Cryoclasm, and Karplusan Strider.
Each card of the five "color hosers" mentions two other colors, just like the Weavers; but in this case the cards affect the color's enemies, and do something nasty to them. If you have a friend who's just getting into Magic, build him or her a deck that uses one or more of these color hosers, and then play a deck of the enemy colors on the other side of the table. Let your friend counter your Kird Ape or blow up your Island. It's a simple puzzle to figure out, but an immensely satisfying one, and a great way to use Tenth Edition to bring new players into the community.