As there already exists a sloppy attempt on my G+ account, I decided to redo it during the past week. It turns out that it was complicated to me to even figure out the most basic tools but after several days and numerous restarts I finally was successful to a degree that I'm satisfied with.
The gradient used in the background is a custom one that I created; it features Fluttershy's normal and rainbowified colors (eight in total).
Pictures of this set: • Fluttershy, pencil line art >>1284346 • Fluttershy, digital colouring (current) • Fluttershy, traditional colouring >>1284372 • Fluttershy Avatar >>1284376