All over dark grey, smoke box, chimney, motion and cab included; the only relieving detail was the red buffer beam with shaded numerals (loco only, never tender) light yellow painted cabside number, and light "eau-de-nil" green "snail". I have seen many pictures of these locos over the years, and most would have "snails" on their tenders, but tenders could be swopped, and running with a plain tender would be possible.
None were ever green. Six of the twenty lasted into the 1960s so a very late repaint in black is possible if you are modelling post 1958, say. However, I never saw a picture of one that was definitely black. Prior to that, they were all grey since the late 1910's. This became, even in CIE times, the "default" livery to the end, not black. Having said that, a combination of dirty oily rags and soot, as well a natural wear, tended to darken the grey so that in many photos it looks as good as black!