Official State Flag of Washington
Washington's flag is the only state flag on a field of green; an appropriate color for "The Evergreen State" (Washington's unofficial nickname).
Legal Description of the Washington state flag:
The official flag of the state of Washington shall be of dark green silk or bunting and shall bear in its center a reproduction of the seal of the state of Washington embroidered, printed, painted or stamped thereon. The edges of the flag may, or may not, be fringed. If a fringe is used the same shall be of gold or yellow color of the same shade as the seal. The dimensions of the flag may vary.
Note: Washington is the only state that is named in honor of a United States president.