Essentially, ubiquity is the answer to the question What percentage of my decks are going to play this card? While this question immediately has implications regarding color identity (even putting aside power level, chances are that your colorless cards will have a greater deal of ubiquity than your colored cards), it is important to look beyond just the percentage of decks that can play a card
On Energy cards: the stamp is in the top-right, next to the word "Energy"
Magic: The Gathering was first released on August 5, 1993, making it the first-ever trading card game (TCG)
Playing against a powerful Planeswalker deck
Waterbend is a cost and always includes an amount of mana that must be paid
so even if you have access to the entire set (which is by no means a given in 1997, the internet wasnt close to the repository of human knowledge that it is today), you would need time and guesswork to make sense of the story