Assume that a dielectric object is pure red,which is litted by a pure white light(or even more white).Then its highlight would be pure white.
But if the object is a conducter or metal,the highlight's color should be pure red.
According to the thread above,this is because of light reflect on the surface of metal,but subsurface of dielectric.
In my view,when a gold is gold,not the highlight is gold but all surface looks gold.What means all the light comes to the surface of the metal then reflect in a color,not only the highlight part.
From some pictures,I found that the metal's highlight always don't have color,but appears white.
For dielectric have no specular reflection,only have diffuse or subsurface reflection,and the subsurface absorb some colors and reflect others.Obviously,highlight is part of the reflected light and why the highlight is white.Shouldn't it be colored?
otherwise,in our daily life,metal's highlight often apears to be white,and why.
A big guess about these:maybe the dielectric's highlight is not pure white,but a color at (280,270,270),but we could not recognize and that "looks" white.And this is suitable for conductors.
The highlight turns to be a highlight is just because of the value is above(255,255,255) I think.
So the color get less saturated and the value get brighter,and result in a white.
This is just some thoughts,if I were wrong,please put me right.
Hope I express clear,and expect real discussion.