You might have observed it while travelling, but do you know why certain types of vehicles follow a similar colour-text code for the number plate and the others follow a different one? There are various parameters that decide which vehicle bears which coloured number plate.
White number plate
Cars bearing black lettering on a white background are private vehicles. These are used solely for private purposes and can't be used for any commercial purpose.
Yellow number plate
Commercial vehicles such as trucks and taxis have a yellow number plate with black text. These vehicles can be used for any commercial purposes. However, the driver of the vehicle must have a commercial driving permit.
Black number plate with yellow lettering
These are commercial vehicles available on rent for self-drive. These cars can be put to any commercial purpose without the limitation of the driver having to own a commercial driving permit.
Light blue number plate
Vehicles belonging to foreign consulates bear white lettering on a light blue background. These number plates bear UN, CD or CC, which stand for United Nations, Diplomatic Corps and Consular Corps respectively.
The number following UN, CD or CC refers to the country (as given in the list below)
Red coloured plate
The President of India and governors of states travel in official cars without license plates. They have the Emblem of India in gold, embossed on a red coloured plate.
Number plate with upward pointing arrow
Military vehicles follow a unique numbering system unlike any other license plate numbers. The numbers are registered under the Ministry of Defence, New Delhi. The first/third character is an upward-pointing arrow, known as a Broad Arrow, used in many parts of the British Commonwealth. The two digits succeeding the arrow show the year in which the Military procured the vehicle.