This 3" Dryococelus australis (Lord Howe Island Phasmid aka Stick Insect) is a juvenile, living in a case at the Lord Howe Island Museum. Adults are dark brown. It has an amazing story, thought to be extinct until 24 were found on a tiny nearby island, Ball's Pyramid. Researchers in Melbourne and San Diego are breeding them. (This is only the second time I've included a photo of a captive animal on iNaturalist.)