I have my stuff in the black finish. I have always added a stripe of white sticky paper (actually a cut bit of lettering tape) across the knob at the "invisible' pointer spot. So from a distance i can see exactly where the knob is. i used this on my prior preamp, an Adcom 750, and also have the same effect on my Audio Research Sp-15 on the dB, vol, selector, and phono resistance loading knobs.
On my Bryston BP-26 i have the marking on the Volume and the selector.
It is just a slender slip of tape that can easily be removed, but is VERY useful when it is there on the knobs.