The red light is to indicate that a "unsafe area" . Pretty irrelevent in normal (flying ) operations as the U/C and U/C doors area isnt anywhere a person would be . However , during maintenance , when U/C doors are dropped to carry out inspections and/or component changes, maintenance etc, you would not want to be in the area when the red light illuminates......for instance , doors have been selected to close, or U/C selected up.
There are physical pins which engineers should put in the door locks and U/C downlocks during maintenance to prevent any inadvertant operation, but..... if the lights go on I would not hesitate in getting out !
