This is the forward Master Call Light Panel installed in the ceiling of the cabin. A second one is located aft. These panels exist on all large aircraft for the cabin crew members to be alerted without staying at their seats.
The number and color of lights vary according to customer requested options for the cabin. Some lights may be duplicated to indicate which side of the cabin is affected (e.g. for the passenger call). These panels are not required by regulation, it's to facilitate the work of cabin crew members.
For the B737
The non customized panel of a B737 looks like this:
Source: Boeing 737 FAM
The lights illuminates and chimes are played:
- Pink, HI-LO chime: A crew member dialed the forward station number on the cabin interphone handset.
- Blue, HI chime: A passenger pressed the ATTENDANT CALL switch on the Passenger Service Unit.
- Amber, HI chime: A passenger in the lavatory pressed the ATTENDANT CALL button.
The white portions are not used, there is no light here.
Source: Boeing 737 NG Flight Attendant Manual (D6-27370-6/7/8/900-FAM).
For the B787
- Green, HI-LO chime: Cabin crew call.
- Green flashing, HI-LO chime three times: All call.
- Pink, HI-LO chime: Flight deck call.
- Blue, HI chime: Passenger call.
- Amber, HI chime: Lavatory call.
- Amber flashing, HI-LO continuous chime: Lavatory smoke.
- Amber flashing, HI continuous chime: Crew rest smoke.
- Red: Sterile flight deck (pilots mustn't be disturbed except for safety matters, and attendants must expedite operational activities leaving commercial activities for later).
No doubt in a few years, attendants will receive these indications directly on individual portable devices with more details.
Airbus has its own similar colors and chimes, see: