The Most Flexible Car Paint Shader For Cycles
No, it's not. The car model is one of Blender's demo files listed here: https://www.blender.org/download/demo-files/
It's made by Mike Pan and licensed as CC0.
The paint is composed of small differently colored flakes, so, as a first step, turn Flake Color Mismatch and Hue Shift fields to 0.000 and go from there. These are the two main controllers for hue differences between flakes.
On the downloaded blend file, check the compositor nodes and import/append those to your own project file.
Although I made this specifically for using with Cycles, there is no reason for it not being able to be used with Eevee. It might look slightly different, but still, not bad.
Update: Recent Blender versions (3.3 onwards) have "broken" Eevee previews (they show up as pink textures). Although this is the case now, Cycles functionality was not broken in any way.
Turn up the samples for your viewport slightly. That is a result of the way path tracing works and how the paint is composed of tiny differently colored points, but, after a certain still low number of samples (I'm using 256 in my case), the color doesn't go noticeably lighter beyond that. Of course, situations change depending on your scene's lighting.