There is no one answer to this question as there are many possible reasons why Egyptians may have worn green eyeshadow. Some possible explanations include that green eyeshadow was used to protect the wearer's eyes from the sun or harmful glare, or that it was believed to have magical properties that could ward off evil spirits. It is also possible that Egyptians simply thought green eyeshadow looked beautiful and fashionable. Ultimately, we cannot know for sure why Egyptians wore green eyeshadow, but it is an interesting topic to speculate about!