Artwork & Concept: The Mewtwo VSTAR card is particularly famous for its perspective
These topics are more generic, such as manabase, ramp, card draw, etc
Legends like Graaz, Unstoppable Juggernaut who turns all your creatures into 5/3 Juggernauts, or the new variant of everyones favorite Phyrexian Angel, Atraxa, Grand Unifier, which gives us a Niv-Mizzet Reborn effect that looks at cards types instead of colors
Discard effects also work significantly with this kind of ability, which reminds me of Dauthi Voidwalker at a bigger scale
And two, why would you do it if one had that much Silly Putty
One way to do multicolor cards is to find an overlap between the two colors and push the power of the cards with the idea that if you spend both colors that can do the effect, you get something stronger than any one color could get