I collect G-Shock's and each one has a great selling point, this ones is the night light. It is red.
Red lights are used in astronomy because a humans eyes can take up to 30 minutes to adapt the dark. Most shades of light at levels bright enough to excite your cones will knock out your eyes out of darkness adaption for several minutes. However, your eyes are fortunately rather insensitive to pure red light when they are dark-adapted. What this means is that if you use red light that isn't too bright, you can excite your eyes enough to read by. In other words, you can then switch quickly between scotopic and photopic vision without having to wait for your eyes to adjust to the change in light levels.
So this watch can be used in the dark by anyone that want to keep their eyes adapted to the dark, and it also has the usual G-shock features such as waterproofing, toughness, alarms, different time zones, etc..