According to ComicBook.com on Saturday, director of "Guardians of the Galaxy" James Gunn had received a gift from Marvel Studios of a prop piece of one of the Infinity Guantlet's Infinity Stones. The color of the stone happened to be red, whereas in the film, it was purple Gunn gave clarification on this after fans had taken scrutiny of this difference.
The gift to Gunn was captioned "That was a pretty good plan". Perhaps this may have been a reference to the 12 percent plan, though only partial, Star-Lord had when trying to concoct an idea to defeat Ronan the Accuser. In the comic books, the particular Infinity Stone in question was the Power Gem and was also red. Turns out Marvel Studios doesn't intend on keeping the "color code" to the corresponding swatch exactly in sync with the Marvel Cinematic Universe. Turns out, Gunn stated that the color simply worked for "Guardians of the Galaxy" as the color of red was already designated for "Thor: The Dark World."
Gunn made his clarification to Facebook user Gareth Dawes:
"The power stone is purple because the aether already took red. And it's a better color for GotG."
Massive debates on the Internet had gone back and forth when director Gunn had announced the Power Gem and it was questionable if it was actually that specific gem since the color had seemed to contradict his function. So far three of the six stones had already been revealed.
One of that likely have been contained in the Tesseract from Joss Whedon's "The Avengers", the other having been contained as the aether that called to the universe the Dark Elves and currently under containment with Benicio Del Toro's The Collector, and finally the more obvious purple/comic book red Infinity Stone that Gunn laid to rest it's purpose.
It is debatable whether or not the forth Infinity Stone is the one contained in Loki's staff at the Hydra bunker at the post-credits tease of "Captain America: The Winter Soldier." That being said, one could probably actually confirm that once "Avengers: Age of Ultron" is released in theaters.