[aMorePerfectUnion]

ENoCH
‏ @elenochle

"Rig for Red" is a command used in the Control Room. 
It is used when the boat is going to be surfacing or 
coming to Periscope Depth at night. The purpose is to 
give the lookouts heads up for their eyes to adjust to darkness.

[TexasPatriot1]

Posting blind. Confirmed. Sub control room “rig for red” = night ops at PD or prep to surface.