Pinkamena Diane Pie buried her face in her pillow. Slowly, bit by bit, all color began to drain from the world, starting from her very room.
It started, naturally, with the pillows, creeping out slowly at first, but hastening in its pace as the grey enveloped more and more of reality itself. Before long, her entire room had lost its color. Then the building, and beyond that, Ponyville itself.
The Grey continued to creep without end. Now, out in the open, its relentless pace had finally begun to slow, if only temporarily. Here, ponies and creatures of all shapes and sizes began to attack it. They did all that they could--paint, prisms, mirrors--but in the end, not even the magic of the Elements of Harmony could put an end to the Grey.
An exhausted, monochrome Twilight Sparkle knocked on Pinkie's door. "Pinkie, may I come in?"
"Yeah... I guess... Just be quiet when you do."
Twilight entered the room and dropped a Snickers bar beside Pinkie.
"You're not you when you're hungry."
And that's how the colors you see exist again thanks to a single Snickers bar.