On my 2014-01-18 CET flight ST2114 from FKB to LPA on a Germania airplane, cabin lights were switched from white to blue for takeoff. I recorded this in a panoramic photo.
Granted, on sunset, the sun coming in through the windows made up for a beautiful play of light: Blue and yellow are complementary colors.
Is there a security or technical reason for the blue light, or is it just for aesthetics?