So, last week I talked about an artifact that let other artifacts made colored mana, on the condition that they had that color. There are over 100 artifacts that are colored (most of them White, Blue, and Black because colored artifacts were released as the mechanic for the white, blue, and black faction in Alara), so it's a workable niche.
I often research my designs so I can understand templating and power levels. I ended up looking at the interesting methods that lands and artifacts have used to give players mana throughout the history of Magic.
Hated as they are, these cards have seen more nerdboners than anything should ever have to.
The grandaddy of them wall was the Black Lotus. The Moxes were up there too. The theory behind the lotus, based on conjecture, is that it's only one-use, so it's not that bad. However, dropping a four-mana anything on turn one is a really big benefit. It might be a card advantage issue, where you're effectively discarding a card for three mana (even Dark Ritual makes you pay B for that), but it's still a bargain. I can't even begin to defend the moxes, which are basically lands you can play all at once that hate Nevinyrral's Disk and Shatter.
What's strange is that the first run of Magic also had Celestial Prism, which...
The moxes and Black Lotus were six of the Power Nine that got banned in early Magic history. A cursory search through the next nine Magic sets shows that Wizards continued to work on it. Artifacts like Implements of Sacrifice and Mana Batteries were one-shot artifacts that used the high cost of generating one color of mana from another color (or colorless) mana—known as filtering—to float mana from one turn to the next. Standing Stones brought the mana cost of filtering closer to 1:1, in a repeatable form no less, but at the price of paying one life.
Fellwar Stone looks like it was the first artifact which uses the "limited potential," tack, which provides colored mana, with a restriction on the type. Later, there would be mana generated which could only be used for specific purposes.
Lands also got some attention. Because all lands have the same cost (zero), Rainbow Vale and City of Brass played around to find a competitive exchange rate. Rainbow Vale literally gave itself away after each use. City of Brass charged a single life point for each mana it produced. Rainbow Vale is largely ignored today, while City of Brass got a fitting reprint in Modern Masters this summer. Obviously one mana of any color was worth more than a single life point and less than loaning one of your land drops to your opponent.
And Magic, for the most part, sticks to those approaches to handling artifacts and lands that provide multiple colors of mana: one use, repeatable with a cost, and conditional. I'll more about that next week.