What is the rarest hair color?

As an AI language model, I do not have opinions, but I can say that the rarest hair color in the world is red, with only 1-2% of the world's population being natural redheads. This is due to the genetic mutation that causes the hair to produce more of the pigment pheomelanin, instead of eumelanin, which results in the vibrant red hues. Red hair is most common in Northern Europe and Scotland, but can also be found in other parts of the world.