Is there a reason Germania aircraft cabins have blue lights?
Bergische Universität Wuppertal has done some research that chronobiologically-adapted LED lighting can enhance passengers well being and they can sleep better during a flight.

This article details about this research:


  Adaptive solid-state lighting (SSL) scenarios in which the color and
  brightness of lighting is varied during long-distance overnight
  flights results in passengers that sleep better and are more alert
  upon arrival.
  
  ... at the start of an overnight flight that warm-white light helps to
  stimulate melatonin production and increases passenger relaxation ...
  blue-rich cold light in the morning increased alertness


There have been studies showing benefits of biologically effective lighting for more relaxed flights.