It is amazing how many "experts" (often a state or FRA inspector) claims something is a GCOR or 49CFR rule - like glow in the dark vests, getting on or off moving equipment, etc. Many of these are either common railroad practice, in a railroad's safety rules or special instructions. Then again, the FRA is issuing volumes of rule changes so fast I can't keep up. If the railroad includes it as a rule or rule change, then the FRA can enforce it on that railroad.

Regarding variable switches - Notice no mention is made of them painted yellow:

8.18 Variable Switches
Trailing point movements may be made over a variable switch from either track, regardless of the position of the switch points.
When making a trailing point movement and the switch is not lined for such movement, make sure all wheels of the leading car or unit clear the switch points before changing direction.
During snow storms, ice storms, or other conditions that may prevent a variable switch from functioning properly, avoid making a trailing point movement through a variable switch until it has been lined by hand for movement.

Unless you look in the glossary for the definition:

Variable Switch
A switch identified by a V or a bowl painted yellow.
When trailed through, the switch points remain lined in the position they were forced.

One of the most incorrectly used terms is "siding", which has a diffrenet meaning than most people apply per the glossary:

Siding
A track connected to the main track and used for meeting or passing trains. Location of sidings are shown in the timetable.

Many people incorrectly refer to a runaround or passing track as a siding. There are specific rules for sidings, while other tracks that happen to have switches at both ends fall under rules for auxiliary tracks.

Regarding switch point locks: I have worked on several railroads where the handles were painted yellow. A good reminder, especially if you don't use the switch much. There is a moment of confusion why the switch won't throw until you remember the second lock.

I did find ir in the 2005 BNSF TY&E Safety Rules:

S-13.7.4 Operating Switch Point Locks
When working with switches equipped with switch point locks (so designated by yellow handles):
1. Know the difference between the two basic types of switch point locks.
2. Remove the padlock from the switch point lock.
3. Use your foot only to depress the pedal, which places both types of lock under spring tension.
4. Snap the switch point lock into locking position by returning the switch to the normal position. Inspect to assure the locking position before putting your hands near the switch point lock to replace the padlock. If the switch point lock fails to snap into locking position, reopen the switch and repeat the process.
5. Do not attempt to pull up the pedal by hand or other means. Contact the train dispatcher and report the switch point lock defective. Tag out the switch.
Repair or correct defective switch point locks only if you are a qualified Maintenance of Way employee.