Sorry for the late response. I still had to dig a bit to understand and am still not completely sure if I got it right.
What I gathered is as follows:
- The filament guide states in 4.8.5 to
Use values with a luminosity of 67% to 100% (170-255 sRGB)for metallic materials. So the colors that I chose for the examples are very unrealistic for real metals. F0 is the base color of the metal and the list in 4.8.3.2 shows colors that are in the mentioned specs. - IOR values for realistic clear coat are mostly around 1.5, maybe between 1.3 and 1.6. The high values from my examples are very unrealistic for real materials so they cannot be compared to the real thing. 4.9.1 states that
air-polyurethane interface has an IOR of 1.5.
I verified that the materials look somehow like I would expect when I stick to these rules.
As far as I could understand the color shift occurs because of a shift in the wavelength of the reflected light. It is mainly caused by refraction through the clear coat with far too high IOR values + too dark F0 colors. So if I try to use this as a boost for an effect the color shift is to be expected and not a bug.
Does this sound about correct? If so maybe someone can transfer this topic to Questions. It is not a bug but the information can be useful to others with that problem.