1. After the girl throws this question, the friends need to pay attention to whether she is really black, and then find the right entry point to answer.
2. If the female friend's skin is not dark, you can ridicule that "people with dark skin generally like to tell lies", or you can do some simple science on the skin first, and don't directly answer her questions, such as your sebum layer is thick and you can't see your true colors.
If the female friend's skin is really dark, then look at her usual personality before answering. If she is extroverted and doesn't care, it can be said that "black is black with personality, and black skin is healthy black". If she is introverted, you can say "Maybe you don't pay attention to maintenance" and then recommend a series of skin care products.