Excellent idea - but beware! The bauxite liveries on both are entirely inaccurate at all levels!
First, the H van. Neither these, nor almost any other Irish wagons had black chassis. The shade of bauxite on both is far too reddish, though some of this is due to the fading qualities of modern paint - not to be confused with the fading of older paints. It should have a brown chassis and drawgear, as well as body, and roof. 1 out of 10: the lettering and logo are as correct as you'll get.
Now, the plough.
In GSWR days, as per markings, these were either all black or later, all a very dark grey like loco grey. (Indeed, logo grey might have been derived from this; "normal" wagon grey, which is lighter, came roughly post-1915. If grey, then grey chassis too.
The GSR and CIE painted them ALL wagon grey - again no black chassis, and most certainly not a white roof! After 1970 or so, CIE and then IE painted them all brown - yet again, chassis and all. Never were they anything remotely like the above.
The more reddish shade of brown seen nowadays is a post-1995 or thereabouts invention.
One or possibly two of these were heavily rebuilt and survived into the post-1990 yellow era. Yes, roofs and the lot were yellow.
Black chassis are a Hornby train set invention, and are only appropriate for BR modelling, where wagon chassis WERE often black. Unfortunately, this incorrect livery detail has been widely copied in Irish preservation, where - unfortunately - between Cultra, Whitehead and Downpatrick, correct liveries on locos, coaches and goods stock alike are (at last count) outnumbered about three to one by incorrect liveries.
For modellers seeking accuracy, this is indeed a great shame.