In message , Barry Salter
writes

Nothing. In fac rumour has it that the white aspects are going to be
replaced with blue aspects, to match the blue aspects to be used on the
VLU signalling.

Buuut...If you do that, then they could be confused with lamps
associated with tripcock testers. Fun eh?

Other than white is also a valid TCT colour too , depending on the
location.
--
Steve Fitzgerald has now left the building.
You will find him in London's Docklands, E16, UK
(please use the reply to address for email)