It's so that you don't lose your dark adaptation. See: https://www.nps.gov/articles/dark-adaptation-of-the-human-eye-and-the-value-of-red-flashlights.htm https

It's so that you don't lose your dark adaptation. See: https://www.nps.gov/articles/dark-adaptation-of-the-human-eye-and-the-value-of-red-flashlights.htm https://www.nps.gov/articles/dark-adaptation-of-the-human-ey...