The law states that you are not allowed to attach ANY colour of flashing light to a vehicle other than orange as this represents an emergency service vehicle.
However cyclists and pedestrians ARE allowed to attach any colour of flashing/strobe light including blue and red to their person.
Hope this helps.
It helps, yusstay, but also broadens the confusion - because I take it that the offence of impersonating a police officer over-rides being allowed to have a blue flashing light stuck on my head.
I don't WANT to look like a policeman (although I have enormous sympathy and respect for them), but I do wear a yellow jacket for self-preservation while riding through the jungle of NW London, plus a helmet, plus black trousers (as it happens), and I am 'big looking' (although in the proverbial fight, the paper bag would definitely come off best).
But I do have a feeling that sticking a flashing blue light on the front of my bike might draw unwanted attention from the remnants of my local police force! I don't want to waste their time, and they might always look too closely at my unused off-road button...
Allen, Wisper 905, not a blue light in sight.