"Shade" of the lighting comes into safety perception though if you look at the research. How the interior responds (e.g. TfL 345s where TfL did tonnes of work on this) to the light helps mitigate this.It's perfectly possible to have a the lighting a shade warmer without impacting safety and maintaining or even improving attractiveness. Class 345 lighting doesn't feel as harsh as Thameslink does, although that might be because the interiors are also quite different.
There are loads of poor quality (cheap) phosphor choices out there and LED can enable far less harsh daylight/cool shades if done properly. I suspect most people issue is with some of the cheap phosphor choices to save 5p on fluorescent tube.
Another key element of lighting design is ideally to have the light reflect off / refract through surfaces before getting to the user to make the polarisation more uniform and less random which makes the light appear far less harsh. (Again done well by TfL on the 345s)
In terms of lumen efficiency cool / daylight shade white can have about 7-8% higher apparent lumens/watt in terms of what the eye can perceive.
Hence the optimised lower carbon choice is slightly dimmer cool/daylight shades.
