This .Blend file includes:

A photoreal, PBR car paint material, made procedurally.

A material that can be changed on the fly, it can use up to 3 colors simultaneously. all of which can be any color of your choosing.

requirements:

no knowledge of shader nodes is required, it is a hands-free material that works immediately. 

ZERO UV unwrapping is necessary! it uses procedural alternatives.

tips:

If the shader has an odd scale, make sure to apply the scale of your object.