Blue and orange are complementary colors, so I can see why the designer would go for that contrast. The orange looks really nice with the colors of the spring tulips in the main image. However, I’m sure the background came before the image in the site building process, so this image may change in accordance with the background colors.
As I said in my mini response, the active and saturated orange was still a surprise to me. I expected a more patriotic red color to match the Chicago flag and local government feel. This orange reminds me more of a local school website—maybe their team colors. I may be thinking along the lines of the Chicago Bears as well.