red
Red light is the slowest, biggest light wave in the visible spectrum. It just kinda of lazes around and bumps into things. Since it’s so slow, it’s perfect to make things just barely visible and not draw attention to itself, just like in every sci-fi movie. Yes, it means danger as in do not expect it to do much or be too active. Slovenly, actually. It excels at giving just enough light to recognize our prurient desires, lustfully illuminating (just) the deepest carnal desires we all carry around with us through our lives.
red flags
red in the face
red herring
red carpet
Outside the Western world, red has different associations. For example, in China, red is the color of prosperity and happiness. It can also be used to attract good luck. In other Eastern cultures, red is worn by brides on their wedding days. In South Africa, however, red is the color of mourning.
Red can actually have a physical effect on people, raising blood pressure and respiration rates. It’s been shown to enhance human metabolism, too.