from another forum. Someone called VOSA and asked and were put in touch with the agency that covers this:
The result of the enquiry is:
Dear Mr Wayland Our understanding is that paint such as 'glow in the dark' paint would not be classed as a lamp or reflective material and therefore it would not need to conform with the requirements of the Road Vehicles Lighting Regulations 1989, as amended. However, as I'm sure you'll understand, only the courts can provide a definitive interpretation of the regulations. Regulation 100 of the Road Vehicles (Construction and Use) Regulations 1986, as amended (C&U), requires that a vehicle is maintained at all times in such a condition that it is not likely to cause a danger to the user of the vehicle or other road users. It is possible that 'glow in the dark' paint may cause a distraction to other road users which could be considered to be a danger. Yours sincerely Jillian Smith DfT - Transport Technology and Standards