This topic is one of those that will answer your probable question as soon as you land around the streets of a new country.
The way each country or even state (like the USA does) deals with it is easily noticeable.
What happens in Brazil is that there’s one law for the whole country, no matter where you go all cars must have license plates(like the one below) attached to the front AND the rear.

Here, both license plates are the same color, that was one thing I asked in Hong Kong, the vehicles there have white plates in the front and yellow on the rear.
Different vehicles have different colors:
White: passenger cars or motoebikes.
Red: cargo vehicles.
Blue: embassy cars.
Black: collector’s cars, older than 30.

All plates(color independant) have 3 letter digits and 4 numeric digits.
Each state gets an intervall of letters that will begin the license plate.

The plate will be the car’s plate, forever, whenever you sell the car, the license plate will go with it. I know that in some countries the driver keeps the license plate and can use it in his new car.
The motorcycles only have license plates on the rear. As you can see below.




