315850 was last used in autumn 2008. I hope they get that one back on the running rails soon - it's been a fair old while!
What I do find surprising is that they haven't repainted their 315s yet. I know they had 317s in the debranded 'one' livery and they did get repainted, but on the whole the 315s are in poor external condition.
I have heard somewhere that due to their franchise running out early next year, only the 317s & 321s are being repainted. No more repaints are being done to the diesel fleet (aside from 156419 in full NX white & grey colours and 156402 in Chapelfield Shopping Centre advertising livery with NX stickers covering up where it used to say 'one' in very small letters, all 153/156/170s are in a curious mix of either Central Trains, Anglia or ex-'one' livey).
360115 was revinyled into full NX white & grey when the rebranding took place but all the others are still in First Group bule with NX white stripe. The blue paint is vandal-proof so can only be removed with a sander and cannot be painted on top of (graffiti proof paint - yes!) so the 360s will remain in these colours as 360115 was only done as it was part or the comapny launch, which was a publicity stunt effectively.
I get the impression that NXEA don't care about the 315s, as all remain in the ex-'one' livery, although I think it suits them rather well.
A couple of 90s have been repainted into NX white & grey colours and 1 full coaching rake has been done, although this has since swapped bufet cars with another coaching set for some reason as it had an ex-'one' buffet car and an ex-'one' set has an NXEA buffet car. The writing on the car closest to the loco seems to have run as there is blue paint smeared down the side of the coach and it doesn't say National Express anymore there.
321446 has the worst intentional (i.e. not graffiti) paint-job of any train I have ever seen in public service and I hope to god it gets repainted next.