Why is Landing Altitude displayed in amber on B777?
The Boeing 777 is a very automated aircraft.  The takeoff altitude, landing altitude, and cabin pressurization altitude are all automatically set when you enter the departure airport and destination airport in the Flight Management Computer. 

The EICAS message ALT LDG appears when the FMC is not controlling the landing altitude. This can be caused by one of three different conditions:

1) There is no destination airport entered in the FMC

2) The FMC landing altitude function has failed

3) The LDG ALT knob has been used to set the landing altitude manually 

It is also normal to see ALT LDG after landing when the route has been dumped.