The law on under Car/Quad Lighting:

The 1989 Road Vehicle Lighting Regulations cover the whole issue of vehicle
lighting. In short, the regulations state that there should only be certain light
emissions that apply to certain external areas of a car.

For example it states that constant light beams must be clear at the front of a road
vehicle (with the exception of the indicators) and red at the rear (Again with the exception of the indicators).

Blue is also associated with emergency vehicles and is therefore illegal for use on the public highway, But is fine for display use on private land.

Extreme caution should be used if displaying your glow on a public high way - it is illegal if a bulb is visible, But if your lighting kit is fitted correctly you do not have a problem.

As the law stands, colours other than blue are technically legal for use on the
public highway, as long only a glow is visible and not the actual bulb itself.

Advice would be to use your common sense on the issue and make informed
decisions from your own experience and others around you.

It is up to police discretion how far they will act in each instance, so if in doubt turn it off!

Just use your common sense and you should be fine if you have led washer jets
don't have red ones facing forward or red side light bulbs as the police tend to not
like this and it may result in you getting handed a £30 fine.

key points:
Only glows no visible bulbs or tubes,
Blue lamps are not permitted on the public roads,
forward facing red led washer jets are a no go