Interesting.

Food for thought:

When working around telescopes at night, they use red lights so they don't lose their night vision looking at things for adjustment and so on.

When hunting, I go into the woods using a red or blue light so I don't alert the animals as much and so I retain my night vision.

Using the research used by first responders back in the 1970's they discovered that green and blue showed up better at all times of the day and night and in most weather conditions.  Green was pretty much ruled out because it was already in use on traffic lights and that just wouldn't work.  Red and yellow/orange were also used for traffic lights and tail lights and were blending in with all the other lighting in use so weren't noticed well enough for safety and alerting other traffic of a dangerous situation. 

Using white light to look for 'cracks' and other such discontinuities would tend to bleed out, not be seen because everything else is lit with white light.

To use a color that is some distance away from the level of 'black' or ultra violet light and yet a contrast to white light makes a great deal of sense and may even be easier on the eyes (turn down the intensity of the white light and let the green light shine through with little effort).

So, there may be wisdom in their procedure.  Would be interesting to hear how it goes after a few months.

He Is In Control, Have a Great Day,  Brent