I see what you mean, DiveController.
Several of these vans (four, I think but could be wrong) were actually used as brake vans for a while, so it isn't totally unauthentic. Naturally, in this state it should be technically only black'n'tan, while if converted to a TPO it could be silver or green. DCDR policy at the moment is to paint all coaches green, much the same shade which is close to earlier CIE, and lighter than UTA. The idea is uniformity rather than accuracy, much like the RPSI's Cravens.
You know me - I think anything preserved should look the way it was, but that's just my opinion and I respect those of others....the RPSI's "Harvey" is now, I understand, being painted in Isle of Man apple green, to match a badly inaccurately painted GNR guard's van...there's "uniformity of inaccuracy" for you...but again, having been that youth with paintbrush myself forty years ago, I will never, ever criticise the work of any volunteer in any sphere. Just the colour!
Rant over; back to the TPO: my understanding is that the DCDR will use it as a passenger brake, and to carry children's buggies in. A space for a wheelchair has, I think, also been considered, but I would advise against it as there are only windows on one side, and these vans were NOTORIOUSLY bad to ride in! Noisy and bumpy.....