The old logo was maroon, and supposed to represent cranes, containers and the port itself.
The new iteration is intended to represent air land and sea. They are also supposed to represent the three parts of sustainability: economic development, social responsibility, and environmental stewardship.As one commenter astutely mentions, it's your standard "eco-friendly palette" at work again.
Here's a snapshot I took during a presentation explaining environmental certification agencies. I was struck by the incredibly similar color palette they all shared.The update certainly refreshes the brand, but why such muddy murky colors? Perhaps they were chosen to reflect the grayness of Seattle's rainy weather? What do you think?