Why are number plates different colours in the UK?

UK number plates are different colours front and rear because the law requires it: black characters on a reflective white background at the front, black characters on a reflective yellow background at the rear. That has applied to every vehicle manufactured after 1 January 1973, and it is not a style choice you or your supplier can make. There are only a few legal departures from it: the black and silver plates allowed on some older vehicles, the green flash on electric vehicles, and the flag panel on the left-hand edge. Anything else in a different colour is either a show plate or an illegal one.

What the law says about plate colours

The requirement is set out as a list with no discretion in it. Plates must be made from a reflective material, show black characters on a white background at the front and black on yellow at the rear, carry no background pattern, and be marked with the supplier and the British Standard, which is BS AU 145e for plates fitted from 1 September 2021. There is a second colour rule that catches people out: characters must not be removable or reflective, and on plates fitted since that date they must be a single shade of black. Get it wrong and, in GOV.UK's words, "You could be fined up to £1,000 and your vehicle will fail its MOT test if you drive with incorrectly displayed number plates." Our fuller guide to UK number plate rules covers spacing, slogans and tint alongside the colours.

Why the front is white and the rear is yellow

The two-colour scheme arrived with vehicles built from 1973. The DVLA leaflet INF104 puts the date beyond doubt: vehicles manufactured after 1 January 1973 must display reflective plates with a white background at the front, a yellow background at the back, and black letters and numbers. Before that date plates were the traditional black style, and vehicles built before 1 January 1973 are still allowed to use them.

Neither GOV.UK nor INF104 explains why those two colours were chosen, so anyone stating the official reason is filling in a blank. What the rule achieves is easy enough to observe: both faces of a legal plate are reflective, so under headlights both light up, and the colour is the only thing that tells a driver, a camera or an officer at a glance whether they are looking at the front or the back of a vehicle. Black on white and black on yellow are also the two highest contrast pairings the standard allows, which is the same reason the characters have to be a single shade of black with nothing patterned behind them.

Black and silver plates, and the 1980 cut-off

This is where most of the confusion sits. INF104 is specific: vehicles manufactured before 1 January 1973 may display traditional "black and white" number plates, meaning white, silver or grey characters on a black plate, and from April 2020 vehicles manufactured before 1 January 1980 can display them too. Two conditions come with it and both have to be met: you must have applied to the DVLA, and the vehicle must be registered in the historic vehicles tax class.

The trap is that the tax class keeps moving and the plate date does not. A vehicle can enter the historic tax class once it is over 40 years old, on a date that rolls forward a year at a time, while the black and silver cut-off stays fixed at 1 January 1980. So a 1983 car can sit in the historic tax class, pay no vehicle tax, and still have no entitlement to black and silver plates. If your vehicle was built in the 1980s and someone offers to make you a set, they are offering a plate you cannot legally use on the road.

The green flash on electric vehicles

The one addition of colour in recent years is the green flash. GOV.UK lists it among the things plates can also do, for a zero-emission vehicle, and INF104 gives the detail: from 8 December 2020 eligible zero emission vehicles are permitted to display a green flash on the left-hand side of the plate. It replaces nothing the law requires and does not change the white front or yellow rear; it occupies the same left-hand strip a flag would. Our green flash number plates are printed as part of the plate face rather than stuck on, and it is for fully electric vehicles, so it should not be added to a plate for a vehicle that does not qualify.

The panel on the left: flags and national identifiers

That left-hand strip is the other place colour is allowed. One of four flags is permitted — the Union flag, the Cross of St George, the Saltire or the Red Dragon of Wales — with a national identifier beneath it from a fixed list: UK, GB, ENG, SCO, CYM or WALES. The layout rules are tight: the flag must sit above the identifier, neither can be on the plate margin, and neither can be more than 50 millimetres wide. The blue panel with gold stars that older cars still carry was the EU identifier, and it now has a practical consequence abroad, because a UK sticker is required unless the plate carries the UK identifier with the Union flag. The rest of the printing on a plate is covered in our guide to the text at the bottom of a number plate.

Coloured, tinted and two-tone plates are not legal

Anything that changes the colour of the background or the characters takes the plate outside the standard. The characters must be a single shade of black, not reflective and not removable, and the background cannot carry a pattern, which rules out tinted acrylic, coloured or neon characters, and two-tone or shadow effects inside the character itself. Plates like that are show plates: fine standing still at an event, not road legal, and an MOT failure.

Raised characters are a different matter, because depth is not colour. GOV.UK lists 3D raised characters among the things a plate can have, which is why 3D and 4D plates are legal when the finished plate meets BS AU 145e: black acrylic characters in the correct font, size and spacing, on a reflective white or yellow background. Our 4D number plates page sets out how we build them to that standard.

What this means when you order plates

Every plate we make starts from the same place: a reflective BS AU 145e plate, black Charles Wright characters at the size and spacing the rules set, white at the front and yellow at the rear. That is true of standard printed plates, of laser-cut 4D plates and of the Outline style, because the style changes how the characters are made, not what colour they are. Plates can only be made up by a registered number plate supplier, and we are one, working from County Durham. You can see any style on your own registration in our number plate builder before you order.

The colours, then, are settled by law. The characters are not: the letters and numbers are the one part of a UK plate you get to choose, and a private registration is how you choose them. Whatever goes on the plate, it will still be black on white at the front and black on yellow at the rear, because that is the only combination that is road legal on a vehicle built after 1 January 1973.