Purpose of red Mars Light and Beacon on F40PHM-2s?

[Deval]

While going thru some old pictures, I noticed the F40PHM-2 locos working on the BN line have red beacons next to the orange one and a red mars light next to the white/clear one on the roof.

Older photos show them still installed, but I have not found a photo of either in use. What was/is the purpose of the red beacons and Mars lights?

[c604.]

The red beacons are for freeze protection. When the units are shut down and plugged into wayside power at outlying yards, they have a layover system that keeps their fluids warm, batteries charged, etc. in the winter. If that system fails, the red beacon will activate to alert nearby employees before any damage occurs.