The all black schemes were to do with reflectivity. They certainly did stand out better at low level than did the earlier Red/White/Grey.
The Dominie had a tendency to vent fuel at high fuel weights on hot days. Had the wings been painted black it would have exacerbated this problem, hence they were painted white.
Additionally it was judged that, had the fuselage been all black then the cabin would have become unbearably hot (especially in view of all the extra electronics fitted to the post DAU aircraft). Thus the white roof.