So as to not derail another thread where a discussion on IOR was emerging , I decided to put this here for others to see the results and tryout their own experiments.
So basically if you want to make a material have some sort of iridescent/pearlescent look or even if you at best are trying to fake some IOR feel then clearcoat and specifically clearcoat reflection values are what you are looking to use.
So here is a model with a clearcoat on , a tint value but clearcoat reflection set to 0 :
here is the exact same model with the clearcoat reflection set to maximum:
Notice the color variants!
Take note the base material roughness is 0.5
The clearcoat roughness is low 0.125
these value matter to get the best results but play around with it your self and get your plain diffuse colors to come to life