Hi Maks @matz17 ,
“if I wanted to make the grunge color fully black and saturated, how would I go about doing that?”
First, for pure black and white and all greys inbetween, the Saturation is always 0. (Actually, Saturation doesn’t even make sense, with pure black.)
Second, the Principled BSDF won’t give a black result, if you just make the Base Color black; some light will still get reflected:
