Green sun

Due to the nature of black body radiation, a star cannot be green on its own. However, a green tinted star is possible if there are oxygen rich gases blocking some of the star light. This can filter out certain colours being emitted, giving the star a greenish colour. This has been observed in some planetary nebulae. However, these types of nebulae are the result of giant stars shedding their outer layers. Any planets nearby would be inhospitable for millions, if not billions of years, and once any living things do emerge, the nebula would have likely dissipated.