Got more info on it, having had tea, and searched archives in the untidy cupboard behind me.
The DWWR withdrew it in 1891 and sold it to W M Murphy & Co., a contractor. Murphy was engaged in building the Bantry extension of the CBSCR at the time, so it is likely that it ended up down there somewhere. There seems to be no further record of it - at some thirty years old by the time the Bantry line was open, Murphy probably scrapped it. It had the name "Oberon", but never carried a number.
My grandfather was born in 1880, so if he did take that picture, he'd have been very young (11 at most!). Perhaps he didn't, in which case I have no idea who did, as the negative is in among old family photos which he certainly DID take. The earliest photos he is known to have been responsible for date from about 1905.
So it remains an item of interest!
Regarding livery, DWWR locos were green at first, but some at least (obviously including the above) painted a red colour for a while in the late 1880s / early 90s - but lined black after that until GSR grey appeared in 1925.