Okay, so… what are the six stones, and where have I seen them before?
"Before creation itself, there were six singularities, then the universe exploded into existence and the remnants of this system were forged into concentrated ingots... Infinity Stones."
— A blonde-haired Benicio Del Toro in Guardians of the Galaxy
That’s the most succinct explanation we get about the infinity stones in all of Marvel’s first 11 movies. The Big Bang’s leftovers are represented by six colored stones with powers that don’t otherwise exist in the universe. Each has its own name: space, mind, reality, power, soul, and time. We've only seen the first four on screen so far, with soul and time still awaiting their on-screen debut.
TESSERACT (SPACE STONE)
AETHER (REALITY STONE)
ORB (POWER STONE)
LOKI'S SCEPTER / VISION (MIND STONE)
Aren't the infinity gem colors different in the comic books?
Yes, but even in comics, the associated colors have changed — especially in more recent issues. There have also been, at times, additional infinity gems, because why not? There’s no significant reason why the infinity stones are a certain color. According to director James Gunn, the Power Stone in Guardians of the Galaxy was purple because "the Aether [in Thor: The Dark World] already took red." The only thing that's remained consistent is the color palette: red, purple, blue, green, yellow, and orange.