Yes makes the end doors stand out better for the guard due to the end doors being white on dark blue and harder to tell than the blue on white of the 331’s. It’s a trial at the moment.It’s been mentioned that it’s to assist with guard’s duties to help see if the train has been fully platformed.
The alternative was a light under the steps at the end doors which light up when the train is put in neutral at each station stop. Would help at night but the union are happy with yellow doors for the trial.