This is the old "lunao.png" from the Anonymous Archive, with a fixed colour for the hair shadow. The original hair shadow transparency had picked up a light human skin tinge, so it didn't work as well with darker or bluer pony hides.
The earring is not part of this hair: it's one of the standard ones.
I do not know who the original author is, sorry.
Princess Luna Static Hair 1.0 by AdrianMcClean
Luna from My Little Pony, Series 2+. Anonymous Archive's "lunao.png" with fixed shadow colour.