Is there any illegal color for a car?

There is no illegal color for car body paint itself in United States and most countries, you can paint car any color including pink, gold, matte black, neon, but there are restrictions on colors of lights and reflective features that can make certain color combinations illegal. For example, you cannot have red or blue lights on front of car that imitate police, as red and blue flashing lights are reserved for emergency vehicles, you cannot have red lights visible from front, only white and amber allowed front, and you cannot have white lights visible from rear except reverse lights. You cannot have flashing or neon underglow in some states, especially red, blue, or flashing underglow may be illegal while driving. You cannot paint car to look exactly like police car with markings if you are not police, as impersonation is illegal. Matte or very dark tint on windows may be illegal beyond limit. Some states restrict highly reflective or chrome mirror finishes that can blind other drivers, though not outright illegal color but may be considered unsafe. In some countries, certain colors may be restricted for taxis or government vehicles. So body color itself, like bright yellow, lime green, is legal, but light colors and impersonation are regulated. Check local laws for underglow and light colors.