I’m unsure who did this coloring, but I was able to find an original sketch posted in to a draw thread on /mlp/ which was an /r/ to be colored.
 
I can’t seem to locate this anywhere else, so I’m just tagging the artist by the name listed on the only source I’m able to find. Hopefully someone knows who did the coloring/outline of it.
 
Original sketch: http://sta.sh/01qu6w3igxm4]
 
Alternate coloring by rainbro-doshie(seems to go by the handle ‘Rainbow-dosh’ on derpibooru: http://rainbro-doshie.deviantart.com/art/1384552897183-color-413817870