Current 4D number plates are technically legal so long as they are in the correct font and the correct background colour eg. White on the front, Yellow on the rear. It is really important to make sure that 4D plates meet the strict criteria as set out by the DVLA as you could be fined up to £1,000 and if you have a private plate, the DVLA could withdraw the use of this number plate from yourself. It is advised that you always use a reputable number plate dealer for obtaining 4D plates.