This has been discussed on another forum I use where members have been confused and this is what was posted:
European law states that you can legally use blue-tint 'xenon' type bulbs (hence they are sold in UK and are CE marked) but UK law states that headlight colour must be white and below a certain brightness. (Normal bulbs are 60w) The police tend to go by UK law, rather than European so will not hesitate in pulling you for it. A court will find in your favour as European law overrides existing member states laws. The best thing to do is carry the CE marked bulb packet around with you and either plead ignorance or politely explain all about European law to the police officer who pulls you!
Sidelights or front position lights have to be white or yellow. Depending on the other lights on the front of your car, you may be able to argue that the green lights are extra optional bulbs (like washer jets neons "****** lights") so could in theory be any colour other than flashing colours, blue or red. You would have to argue that other lights on the car were acting as your sidelights. However, you may have to argue this all the way to court!
As with neons, for other lights you have to obey the general rules:
You cannot display red at the front.
You cannot display anything other than red at the back.
You cannot display blue anywhere (you may be confused with a police car).
You cannot have flashing lights (except indicators).
