Green is the color of restart and growth and for me represents new features in software development. New projects typically have a harmonical architecture and are stable – both properties which are often associated with green color. If you think, green stands for healthiness and hope, you’re also right. Developers like developing new software from scratch, which is greenfield development (the opposite is brownfield development).
In other areas, green means ecology and nature, but green may also be poison. Green means “go” in traffic lights and green is the color best visible for human eyes.