If you would draw a card while your library has no cards in it, instead return a creature card from your graveyard to the battlefield
There are no inherent benefits to having two specific colors in a deck outside of those colors' commonly used gimmicks - so Inking more cards for Sapphire, drawing more cards for Amethyst, having more Singer characters for Amber, and so on
These can be a variety of shapes, colors, and styles which adds or subtracts value from a card
Incredible Super Strong, Mrs
Load up your graveyard with one-mana cyclers, then cast a pair of Flares to win the game
And a Negate is never useless later in the game as a top deck, unlike the Modal lands where a tapped land wasn't that heavily desired later and the spell isn't playable