Contrary to your and the IL lawyer's erroneous classification about this, professional (and college, and high school and pee wee) sports teams' team colors isn't a copyright issue. This is a trademark issue, or more specifically, it's a "trade dress" issue.
Versions of this same question is asked on Avvo so often I have a prepared answer for it. Here goes:
Colors are also available for anyone to use. But if you use a combination similar to the "trade dress" of what some sports team uses, they'll sue you for infringement. There's no magic formula that exists that allows trading just enough on a sports team's "trade dress" to get a team's fans to buy their products, yet is just different enough to not get them sued. What if they use only the name, in a different font. What if they use the colors but no name. What if they use a different version of the team mascot. And so one.
Teams own their trademarks in the classes for entertainment services, clothing, toys, etc., including their team name, plus the colors. They also own the trade dress: the particular configuration of colors (plus their team name and logo using its font in the same size and placement as where their uniforms place it, etc. etc.) that's acquired what's called "secondary meaning" in the minds of consumers. That's what makes the trade dress valuable and is why you want to use it. You're free to use any city name and colors you want for any purpose, BUT just not in a way that recalls the products of any rightsholder and confuses their consumers so that people buy your products under the mistaken belief that they're the offical products of the team. So what you want to ask yourself is: DOES YOUR INTENDED USE CAUSE CONSUMER CONFUSION? If your use calls to mind some other user because your use is similar enough to their use and might confuse some buyers, chances are good that it's an infringement. Consult an IP lawyer to run your intended use by them before you market anything.
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I would be a risky trade dress issue, because you are dressing up your products sold in trade in order to divert souvenir sales from the NFL to yourself to trade on the enormous reputation built at great expense by the NFL. If you do enough to make your product appear to be associated with an NFL team, you have done too much to be free of risk. Will the NFL investigators and attorneys come after you? Depends on whether you affect their sales enough to be noticed. If you do, you will be given an opportunity to stop and it will be done in the way that the NFL attorneys think will most likely make you stop. That could get very ugly and expensive for you.
I am not your lawyer and you are not my client. Free advice here is without recourse and any reliance thereupon is at your sole risk. This is done without compensation as a free public service. I am licensed in IL, MO, TX and I am a Reg. Pat. Atty. so advice in any other jurisdiction is strictly general advice and should be confirmed with an attorney licensed in that jurisdiction.