Hi,
Sorry about the transposition of the regulation date. I looked at EU regs as this is a multinational forum and they are applicable to the UK. If you meet the EU reg and the UK regs do not cover the exact situation, you cn at lease claim good practice which should cover you for any of the general clauses.
On Blue lights regulation 16 says,
"16. No vehicle, other than an emergency vehicle, shall be fitted with–
(a)a blue warning beacon or special warning lamp, or
(b)a device which resembles a blue warning beacon or a special warning lamp, whether the same is in working order or not. "
It is also aginst the uk rules to show other than a white/yellow/amber light to the front of a vehicle. I know of specific cases (in courts local to me at the time) where drivers were convicted for a: Having a bulb behind a red nose on a mini and b: having red and blue lenses on an american motor cycle that was also painted to to like an american police bike. There were no bilbs, holders or wiring behind the lenses and the backs were painted with opaque paint. The is a general exemption, 4(4), that says painting out or disconnecting unapproved lights is the same as removing them but this specifically does not apply to regulation 16.
There is no current requirement for lamps to have a filament, but filament lamps in required lights must be approved and marked. My old paper copy of the 1984 regs required filaments, but I don't know when it was dropped.
I don't want to get into an argument about this so will end it here, the final say is always in the courts.
Regards,
Robert.