Beyond shape, the colour of a road sign and any backing board it is mounted on provide further information about the road or the message.
Learning this colour system helps drivers quickly judge what type of road they are on and how urgent a message is.
What this sign system means
Blue backgrounds are used for motorway signs and mandatory instructions, green for primary routes, and white or black for local roads.
Yellow backing boards are sometimes added behind existing signs to draw extra attention to a temporary or particularly important hazard, and are common near schools or new road layouts.
What to do when you see it
Use the background colour to judge the type of road or route, and treat signs with a yellow backing board as needing particular attention.
- Identify motorway routes by their blue background
- Identify primary routes by their green background
- Treat a yellow backing board as a sign that extra caution is needed
- Remember that colour supports but does not replace the shape rules for orders, warnings and information
How this sign is tested
The theory test may ask you to match sign colours to road types or explain the purpose of a yellow backing board.
Questions can combine shape and colour knowledge, for example distinguishing a blue motorway direction sign from a blue mandatory circle.
Common mistakes
Learners sometimes rely on colour alone and forget to consider the shape, leading to confusion between similar coloured signs.
Overlooking a yellow backing board, which is meant to highlight an unusual or temporary hazard, is another common oversight.
Test yourself on this one
Road and traffic signs is the biggest category in the question bank with 102 questions, and signs turn up inside other categories too. Work through them free, no sign-up needed.
Practise road sign questionsFrequently asked questions
What does a blue background mean on a sign
It usually indicates a motorway route or, on a circular sign, a mandatory instruction.
What is a yellow backing board for
It is added behind a sign to draw extra attention to it, often for temporary hazards or new layouts.
Does colour alone tell me what a sign means
No, colour works together with shape, so both must be considered to correctly interpret a sign.