Located in Westlake Center, the Blue Trees were painted "aquamarine blue" as part of an international art installation created by Australian artist Konstantin Dimopoulos to draw attention to the issue of deforestation. There are also trees on the Burke-Gilman trail in Kenmore that have been painted blue. The trees aren't actually painted, they're tinted with azurite (a blue rock) and water, so over time the color will fade -- so obviously, it's environmentally friendly.

There is also an installation of the Blue Trees located in Houston, Texas.