I think the black test gear looks fresh and modern and it does make the traditional white/cream instruments look very dated.
However, if anyone has ever done a field trial in hot weather, then the last thing you want to expose to the sun is anything black as it will get very hot very quickly. I always assumed HP used light colours for test gear to help reflect light energy. So in my opinion, this move across to black instruments is a triumph of marketing over engineering common sense.
Maybe try leaving a black scope or analyser near a window on a sunny day to see the same problem. I'd expect a white/cream coloured instrument to stay much cooler.