Yes - this was commonplace in makers’ photographs, to provide contrast. While it was seen amongst a number of British liveries, it was very rare in Ireland for any type of wagon to have black ironwork unless the wagon was black itself, as many early GSWR, DSER & Donegal Railway ones were.
The rule on Irish railways was almost always that ironwork was body colour. There were very few exceptions.
Same with makers photos of locos with white connecting rods, or white rims on carriage wheels - they didn’t run like that.
With no colour photography, black, white and numerous shades of grey were necessary on official works photos to show detail. Once photographed, the item concerned would be painted in its “proper” livery before delivery to its new owner.