Legal Car Bulb Colours For Styling | Automotive Lighting

Are blue car bulbs road legal? This question can be a confusing one. Halogen bulbs that have a Kelvin rating of over 4200K are classed as not road legal. Xenon HID and LED bulbs, however, are slightly more complicated.
 

What makes a bulb non-road legal?

When it comes to the legality of halogen car bulbs, it is the Kelvin rating (K) that really matters. Any halogen bulb with a Kelvin rating over 4200K is not legal for road use, and should only be used off-road.

This is because bulbs begin to produce a light with a slight blue tint when they reach a colour temperature of around 4200K. Blue bulbs are used by the emergency services and therefore need to stand out on the road against other drivers. If everyone had blue-tinted headlights, the emergency vehicles might struggle to be spotted by traffic which could potentially cause many problems.
 

Blue coating

Some manufacturers put a blue coating on the bulb to make the beam as white as possible. As long as this doesn’t push the colour temperature up past 4200K, this is road legal. If your bulb has a coating, you’ll not get as much light on the road as it compromises the light output.

Take a look at this comparison of a bulb without a coating, and one with a blue coating:

What about modern cars?

On many new vehicles including Audi, BMW and Mercedes, new xenon HID lighting can give a very slight blue tint. These are still classed as road legal, as long they are factory-fitted HID lights and not an aftermarket HID kit. HID Conversion kits are not road legal.

The reason why xenon HID bulbs can be blue and still road legal is all down to legislation. As Xenon bulbs became more popular, new laws were created that were more detailed and allow for higher colour temperatures.

Another reason why most xenon HID bulbs are classed as road legal is down to their technology. Xenon bulbs contain different mixes of salts in comparison to halogen. They can achieve higher colour temperatures without the need for a blue coating, which means that you won’t have to compromise on light output.

Find out more about xenon HID bulbs later in this post.

LED bulbs are also now gaining in popularity. If your car does not have factory-fitted LED lights, adding them to your vehicle's exterior isn't road legal. This is because it would be classed as a modification to your car.

Shop LED bulbs here.
 

Which halogen bulbs are road legal?

As a general rule of thumb, if you look at the light produced and it has a blue tint, the bulb may not be classed as road legal and may only be used off road. Street legal bulbs such as the PIAA Xtreme White Plus and OSRAM Cool Blue Intense are perfect examples of bulbs that you can use on the road whilst achieving a great styling effect and crisp white light.

Most maximum performance, standard and longlife halogen bulbs are road legal. If you feel unsure, just remember that you can either:

• Check the Kelvin rating of the bulb – you’re usually looking for 4200K or below.
• Check to see if the bulb has the following regulation: ECE R37. This is the seal of approval that they’re fully road legal.
   

Which halogen bulbs are suitable for off-road use only?

You’ll be able to spot a significant difference between 4200K and higher colour temperatures such as 5000K. Bulbs around 5000K are illegal unless using off-road, and will appear to have a distinctive white light with a slight blue tint.

If you’re after a Xenon HID effect, your best choice is the Philips Diamond Vision range. Because these bulbs have a Kelvin rating of 5000K, they’re not legal for road use. Many people tend to buy them for styling and off-road uses, such as car shows and events.

Shop Philips Diamond Vision here.

If you're looking for a strong style statement, take a look at PIAA Stratos Blue. These halogen bulbs have a colour temperature of 6000K, producing a strong white-blue light on the road.

Shop PIAA Stratos Blue here.

Which Xenon HID bulbs are road legal?

Xenon HID bulbs are quite confusing, as they do produce a much higher colour temperature than halogen bulbs but are mostly classed as road legal. Factory-fitted Xenon HIDs can produce higher Kelvin ratings than halogen bulbs and still be fully road legal. Standard HID bulbs usually run at around 4600K and produce a very bright, crisp white light.

As the HID bulbs move up to around 5000K, these bulbs become even brighter and emit a slightly blue light. If this is the sort of look that you are after, and you have a vehicle that takes HID bulbs as standard, then the OSRAM Xenarc Cool Blue Intense and Philips Xenon WhiteVision gen2 ranges are both a fantastic choice.

Shop all of our styling Xenon HID bulbs here.