You'll note in the photo the unique (to this class) form of the black'n'tan livery carried by several of these engines for a time.
When CIE painted locos plain black, the white bit was limited to the tops of cab ends; it didn't go all around and along the sides, unless tan was present too. Several of the B101 class, for a short time, carried the end-only white flashes, but tan the whole way, and full height at that. There was no CIE roundel included, as far as I remember, and I can't see one above.
Many of you will have noted the absolutely superb job recently carried out by the ITG at Downpatrick, in repainting A39 in black'n'tan. This raises an interesting, but small detail, with regard to CIE diesel liveries. As restored now, A39 has a "roundel" on the side. Generally, when an A or C class loco carried full-height tan, there was no roundel. And very few of them carried full height tan at all, especially in later days (post-re-engining). But A39 was one of those which did! Normally, the tan band would be the lower one for a re-engine A. So, great congratulations are due to the ITG and its members for an accurate research job well carried out. If only so many other preserved items were restored with this degree of attention to external appearance - which is what people see first.
Back to the B101 - it can be all black, like the one at Carrick (though with proper font numerals, not the very thick numbers on it). In this guise, there would be a "roundel". Secondly, it can be same with yellow end patches. Third, it can be as above, a variation not carried by any other loco class, and fourth as above but with roundel and with lower tan strip instead of full height band. Fifth, of course, for some (not all) members of the class, "supertrain" livery.