if the color is black the reflection is 0.its just math.like is described before.the build, that i have posted,i have used for every material in the rebuild scene,with the values from your mat screenshots.
since the reflect color, gives the amount of reflection.for example reflect color 0.5 multiplyed with fresnel, you become the half Fresnel reflection.simple as that.
if you dont use the Fresnel in you shader,(fresnel off) the reflect color should be connected to the fac from the mix shader. if you have 0.5 you got 50%diffuse and %50 glossy reflection then.