This is a generic answer, as I don’t know the details of that locality.
The answer to the question, of what a reversible signal can show (or indeed, a normal direction signal when the reversible signalling is in use) depends on the type of interlocking, if the signal is an automatic or a controlled signal, and if it is a stop signal or a distant signal. It also depends on what the specification was when designed. And if the signal has a ‘emergency’ replacement switch or control at the signal box/PSB/panel/signalling centre/control centre/ROC or other fancy named place...
In some areas, automatic reversible signals were provided. These are reversible signals that show an aspect depending on if the sections ahead of them are clear. I once had a report from a driver (running in the normal direction on the adjacent line) saying that he saw the reversible signal step down from a yellow to a red. This driver thought this was odd, as he thought it should be always be red unless the reversible signalling was in use.
What had happened, is at the previous weekend, the reversible signalling had been in use. Normally the signallers held the reversible signal at red via the ‘emergency’ replacement switch that was provided. But obviously during the time that they were using the reversible signalling, this switch was put in the ‘automatic’ position. When they went back to normal working, the switch had been left in the automatic’ position.
The driver saw the reversible signal step down from a yellow to a red, because a train was travelling in the normal direction on the line that the reversible signal applied to. Hence as the track circuit ahead on the line to which the reversible signal applied, went occupied as a train approached, the signal responded as designed.
For controlled signals, they always sit at their most restrictive aspect (red for stop signals) unless the signaller (or Automatic Route Setting - ARS system) calls a valid route for them. And all the conditions are correct (and proved correct by the interlocking), before they are allowed to clear up (to show) a proceed aspect. This will include making sure that there is no opposing route set or called.
For some systems, automatic signals on reversible lines only clear to a proceed aspect if a controlled signal is routed on to the reversible line. Or the controlled exit signal (to exit a reversible section) is routed (it does not have to actually show a proceed aspect). At all other times, the automatic reversible signals show their most restrictive aspects.
Yet another design has other controls to keep the reversible signals at their most restrictive aspects unless the signaller operated his/her control to enable reversible working.