Found in both Indonesia and the Philippines, rainbow eucalyptus trees really are a wonderful sight to behold. But why are they so colorful? Simple — each shade is a mark of the bark’s age. It starts out green, before turning purple, red, and then brown. The changing colors are due to the tree’s chlorophyll levels, which reduce with age. At any one time, though, the tree can sport all those differing shades, leading to truly spectacular results.