Mana symbol order: the main colour is listed first, and the other two colours proceed "forwards" according to WUBRG. This is what I mean when I refer to "first" and "second" enemy colour.
Each land has an ability relating to the second enemy colour, whch may allow it to enter the battlefield untapped. An extra condition or ability related to the first enemy colour allows the land to produce mana of either of the enemy colours (if it seems slightly off-colour, keep in mind that it relates to the main colour as well.)
I had flavour ideas relating specifically to each land, but as always, my creativity is constrained by the artwork that I cannot find.