Registration Plate Colours

[Sammy Snake]

What is the reason for British number plates being white at the front but yellow at rear?

[KebabMeister]

I can only imagine that the white is so it can be seen clearly.  The yellow being toned down so it doesn't glare from headlights at night.  It also helps differentiate the front and rear of the vehicle (!).

I think they were introduced in 1974, replacing the silver on black plates.

[sddsddean]

The original reason (as KebabMeister intimates) was so that you could tell which end of the vehicle you were looking at. I don't really know why this was thought to be so important, unless the 'nutter' was driving it in the dark with no lights! As far as I know, no other country has a similar requirment for different colour number plates. 

[Hippy]

I think this arises from the pre-existing rule that there should be no white reflectors or lights (except when reversing) on show at the rear of the vehicle. The 70s change was for more legible number plates, hence the reflective background. I think other countries do not have reflective white number plates at the rear.

A white light or reflector should immediately signify the front of an oncoming vehicle, or an obstruction that should be treated as such and passed to its left as seen from your direction of travel (in left hand drive countries).