Final answer:
Red decals on license plates indicate new drivers under the age of 21 as part of the Graduated Driver License program. In New Jersey, they cost about $4 per pair.
Step-by-step explanation:
The purpose of the red decals on license plates, particularly in states such as New Jersey, is to identify new drivers who are under the age of 21 and possess a provisional driver's license. This is part of the Graduated Driver License (GDL) program designed to ensure that young drivers gain driving experience under lower-risk conditions. The red decal must be displayed on the front and back license plates. The cost of these decals may vary; in New Jersey, for example, the cost is approximately $4 per pair.