The token making on this is theoretically better than Vitu-Ghazi, the City-Tree, since the creatures can go in any tribal deck and the colorless cost allows it to do the same thing. Does the fact that the cheapening effect applies to your opponent as well balance this effect, or should it cost ? Or perhaps some colored mana?

It's really a kind of awkward restriction. I'd guess that well over half the creatures today have 2 or more creature types. The really weird part is the types of creatures that are most commonly not getting the bonus: Angels, Demons, Elementals, Beasts, Kraken, Serpent, Wurm and Dragons are but all expensive creatures. Instead, awkwardly, this is giving it's bonus to Goblins, Elves and Humans. Maybe that still makes sense. After all, if this was reversed, you'd need two dragons in play to give the bonus to your other dragons...

Also, I'd argue that you probably don't need the 'helps your opponent' parity on this card. The first ability isn't even ": Add to your mana pool. You may only use this mana on creatures." and that might be weak enough to slap a false Vitu-Ghazi on this thing.

Also: Misspelled 'ore'. ­

It's supposed to be flavorful, but maybe I failed there, or maybe it needs a better name. As a place of advanced culture, it's giving a discount to more "advanced" creatures.
The first ability is better than adding one mana, since it applies to all creature spells you cast. Not only will that sometimes/often provide more than one "mana" per turn, it leaves the land open to use its second ability while still providing the cost reduction effect. You're possibly right, though, that it could just apply to its controller.

I dropped the rarity. Is token-making ability phrased correctly? I didn't know how else to write the "all colors" part.

Hmm, it's a bit tricky to phrase the "all colours" part, isn't it? By analogy with Godsire and Crib Swap, I think your wording's pretty close, actually. Perhaps it should read "Put a 1/1 Shapeshifter creature token with changeling that's all colours onto the battlefield."

I like the idea of a land that's boosting advanced creatures, but I think it'd be fine to restrict it to spells that you cast.

I would have said "that's all creature types and all colours", although I agree Crib Swap suggests it's better to say "changeling".

I think whether or not it would actually say changeling might depend on the set and whether it had changeling.