In the factory they use young pegasus blood to create rainbow.

The lil filly over there is blocked, chained and treaten as consumable flash (ever been into a slaughter house?), it has been cutted, it's blood is falling down, and is used to create colours (aka the background), therefore, colours, life and energy is removed from the pegasus, that's why is grey.



It isnt that hard. You just need to be able to read a bit in-between the lines (of the fanfiction too), not only stop at the "omg so gory" surface.