What do the various lights in the overhead aisle light cluster of a Bombardier Q400 NextGen represent? I took this picture of an overhead aisle light cluster in a Bombardier Q400 NextGen.


Copyright: self

I am inquiring about the role of the bottom row of six rectangular lights. From right to left they are yellow, dark blue, dark red, green, orange, and medium red.

My observation regarding these lights:


The seatbelt light, when lit (and accompanied by a single ping), lights up the green light, for about five seconds.
A double ping, with the second ping at a lower frequency than the first ping, lights up the medium red light, for about five seconds.


I presume that these six lights are intended for communicating with cabin crew. I would like to know the detailed meaning of these lights.
This is the so called &quot;area call panel&quot; and it is indeed used to signal the cabin crew. The colours and their respective meaning is not regulated and depends on the aircraft and aircraft manufacturer.
A selection of colors, manufacturer and type according to airliners:

Boeing / McDonnell Douglas:

Pink - Flight crew to FA call ORFA to FA call
Blue - Call to FA from passenger in seat
Amber - Call to FA from passenger in lavatory
Red (717 only) - Lavatory smoke detector set off
Green (DC-9 only) - Unused, included as a placeholder for an unknown function.

Airbus:

Red - Flight crew to FA call OR (some aircraft only) FA to FA
call
Blue - Call to FA from passenger in seat
Amber - Call to FA from passenger in lavatory
Flashing Amber - Lavatory smoke detector set off
Green (some aircraft only) - FA to FA call


Further down you can read, that Bombardier Dash 8 uses solid green for a regular call and flashing amber for emergency call.
A definitive answer can only be found in the respective aircraft or crew manual.