Well, they could start saving their pennies now, in that case: I would suspect it will likely be a decade before they feel the need to repaint the coaches again; that seems to be the usual 'shelf life' of a paint job for the coaches.
It will be interesting to see if they do, at that point, restore the orange. It may be that, by that time, they will have become so used to the green that they decide not to return to the orange. The nostalgic in me doesn't want to think so, now, but I have a hunch that may be the way it will go.
And by that time, having gotten so used to the green, if they do go back to orange I'm likely to lament the passing of the green just as I did the orange! If, however, it turns out that the new paint job is superior to the former...well, then they ought probably to just retain it.
I have a feeling that this new look is going to end up being a better look for the train, altogether. I may be wrong, but if I had to bet one way or the other, I'd bet that the coaches will stay green.