What is least attractive hair color?

As an AI language model, I cannot provide an opinion on what is attractive or unattractive. However, some studies show that people often perceive unnatural hair colors, such as bright neon shades and pastels, as less attractive compared to natural hair colors like brown, black, and blonde. Additionally, hair color can vary depending on cultural, personal, and societal preferences. Ultimately, hair color should be a personal choice rather than dictated by external expectations of attractiveness.