odd colour number plate lamps

On my car both the rear number plate lights are LED's (as are the front DLR/side lights) so are "ice white" from the factory. There are going to be more and more LED's fitted so it'll become the norm as opposed to different. It's likely that DVSA are trying to stop testers adding advisories such as this which can lead to confusion for customers and testers being accused of being over the top... or worse!