In the story, a scientist discovers that cities have more or less a gestalt consciousness, and that they communicate with each other indirectly through people. He decodes this communication, and begins communicating with a city by having people wear colored t-shirts and go to particular places.
The city he communicates with experiences a sudden and rapid downturn...he "asks" the city why, and the city indicates that the other cities think that "he" is crazy. Why? Because he hears voices from nowhere! Your voice!
Cool story...may have been in Amazing Stories, or Asimov...possibly Omni.
I believe I read it in the mid to late eighties, and it was a short piece in an anthology. I remember the anthology being the smaller, paperback-size like Asimov was, I think. It was definitely a researcher who dispatched volunteers with t-shirts...contemporary, non-fantasy setting. I'm nearly 100% sure on the t-shirt aspect.