I notice when running on the Clinchfield Railroad the signals show the wrong indication when going on sidings where the it's always the top signal when you go in sidings when it should be the bottom one showing the indication. I notice the signal to pass the end of a siding the small signal shows green when on the main when the tall signal should show green if on the main and the small one is for sidings.
Many routes of that era did not have speed boards, turnouts had a standard speed, main line speeds were standard and the engineers would have to “sign off” on the route stating they were competent in that knowledge. a little off topic, but when search for some information when speed boards were/are required, I came across this reference which is really interesting for train operations http://www.cwrr.com/Lounge/Reference/rules/title.html
On which railroad? There is no "always" with US signals, since every railroad had (and has) its own system.
Yes, while today there are some signaling standards, each railroad still has some unique rules and signal aspects, and it can even depend on what region of a railroad you are on. For example, where I live, I have never seen a yellow-over-yellow "advance approach" signal. In its place, the dispatcher uses a yellow-over-green "approach medium" or yellow-over-flashing green "approach limited" before a yellow "approach" signal. Sometimes a single yellow "approach" indication isn't used, but instead an "approach limited". For crossovers in my area, trains are given either a clear (green-over-red) or a medium clear (red-over-green), depending on the speed of the turnouts.