Looking at a compilation of the CSX signal rules, one sees "standard" rules (Seaboard or B&O), C&O rules, and ex-Conrail (NORAC) rules. The ETT for the RF&P sub explains its cab signal aspects. Yet, I don't see anything for the ex-ACL. I know they historically used three-color searchlights. Did they have a the same set of aspects as SAL, or were signals on ex-ACL lines standardized in the SCL, Seaboard System, or CSX eras?
All railroads had their own signal aspect back in the day. Many of them were similar company to company - BUT many were not.
I believe there was a Chicago commuter train derailment 15 or 20 years ago. The engineer HAD been an employee of one railroad and then became employed by another carrier - The signals displayed a indication to move over a crossover at 10 MPH or thereabouts. The engineer 'read' the signal as permitting Limited Speed or 45 MPH or thereabouts. The resulting derailment killed several people.