Supposed to give more prominent under lighting especially when in a pool or source of water.
main tags used were Blue_lighting & Light_from_below
useful tags are dark, low_light, darkness, shadows, very dark, dark background, glowing_water, dramatic lighting
can also change color of the lighting by adding tags like "Green_theme" or "Purple_hue" or "red_water" depending on the color you're looking for
I've noticed with many of my generations, that using the tags for score_9 & score_8 tend to want to make a character stand out more and make them appear brighter, lessening the intended effect. Your results may vary, this is just my own personal experience using the effect.
I've noticed that characters with light hair tend to not work as well as it wants to illuminate their hair. Again, YMMV when trying to get them to work.