I'm a yes and I'm a no.
As a starting point, I prefer if colours are actually accurate to the car in question; that is the hoped attention to detail.However, more important to that is still ultimately the impression the model itself gives as a representation of what it is supposed to be. I don't necessarily demand absolute fidelity (interiors a typical source for this), but as long as nothing strikes my eye as disturbingly out-of-place, then I'm good. So in that regard, I can accept fantasy colours as well - at least as long as they fit the car.Like I have this nice Alfa Romeo Montreal that's painted in this copper bronze colour that to the best of my knowledge isn't a real Montreal colour. But it still looks good on it, so I'll just refer to it as a custom paint job. That's my five cents.