There is/was a small pocket guide that may come up on Fleabay on occasion, Locomotives & Rolling Stock of Coras Iompair Eireann and Northern Ireland Railways by Doyle, O.;Hirsch. Has useful running no's, basic stats and dates of building etc., some pics, but they tend to be smallish and in b/w only.
Have fond memories of WA, found orange and black GMs there too!