Yep, @MarieC is correct about Washington being called the evergreen state.. But whomever named it that has never been to the part of Washington I live in.. I live in the everbrown part. Use to be very arid, very dry, sage brush and cheatgrass, Jack rabbits, lizards and rattlesnakes. The only part sorta green is the color we that have lived here all our lives glow do to the atomic reactors that were built and operated here since WWII. But we are changing do to all land is being taken up with vineyard. Yep, changing our climate for sure. So there you go, eliminate wine and save the planet! I'd rather drink wine and enjoy the change.
You can search state colors and not get much of an answer. Seems odd, every state has a state bird, state flower. Why not a state color?
But back to the point, they are all nice, but I like the blue background the best. It just is prettier to me. More cheerful and I think you can pick the colors, most people would not have a clue about state color, state flower or state bird.