Let’s illuminate the situation.

German flashlights in the 1930s and 40s were equipped with several light filters, each to be used in various situations. This particular flashlight, the Daimon Taschenlampe (flashlight), had several color filters and an option to quickly turn the light on and off to signal in morse code. The green filter was used at night in order to allow a soldier to keep his night vision in case he had to hastily turn it off, and to signify to other German soldiers that may be around him that he’s a friendly.