“He said, ‘We have been thrust onto the national stage, and we cannot lose that momentum,’” Bickerton recalled.  Until then, licensing had been a footnote at Boise State. Kustra decided it warranted a full-time defense department, and he asked Bickerton to run it.  Her first priority was to register Boise State’s trademarks, including the one for the blue turf. To do that, the staff had to prove to the United States Patent and Trademark Office that when consumers thought “blue field,” they thought of Boise State. To make the university’s case, Bickerton submitted articles, travel guides and marketing materials — 141 pieces of evidence in all.  The trademark office rejected the application in 2008, citing a “lack of distinctiveness,” but approved a second attempt one year later after Bickerton argued that the previous year, Boise State had spent $2.2 million on advertising that singled out the field.  But other schools had already noticed that a strange-shaded field could mean increased attention. Eastern Michigan has a gray field. Eastern Washington’s is red. At Central Arkansas, the Bears host games on a surface of purple and gray stripes.  There are about 30 blue fields now across all levels, Bickerton said, including six at other United States colleges, and a variety of colors elsewhere. But Boise State zealously defends the status of its home field, Albertsons Stadium, as the only blue one in college football’s highest division. The university also holds a trademark on the word Bronco — though it has permitted the professional franchise in Denver to keep using it.  Bickerton said that Boise State has received about 40 inquiries for permission to install colored fields since her hiring, mostly from high schools. There is no official application process; usually a phone call or an email will do.  That was the route taken by Central Arkansas and Coastal Carolina, which has a teal field. But other licenses have been awarded retroactively — and in some cases only after an approach by Boise State — because schools began or completed construction unaware of the trademark. Boise State granted retroactive permits for blue turf for field hockey at the University of Michigan and football at the University of New Haven. The university takes such actions because failing to do so could threaten its hold on the trademark, Bickerton said.  Bickerton will evaluate not only a proposed field’s color but also its location, proposed use and the school making the request. She will consult co-workers and lawyers if it is a Division I or II football program, or a school in an area Boise State prizes for recruiting, or even a recreational field at a college in Boise State’s conference, the Mountain West.  Boise State approves most requests “as long as it doesn’t prevent Boise State from getting the best students and the best student-athletes that we’re looking for,” Bickerton said. Those schools that are approved receive the licenses at no cost. The only stipulation is that they cannot in any way liken themselves to Boise State.  A half-dozen applications, Bickerton said, have withered or been denied. A North Carolina high school, in one instance, had its request to install a blue field turned down in 2014 because it shared the facility with a local college.  But Boise State’s authority covers a broad spectrum. Citing a legal doctrine called initial interest confusion, which means Boise State has the right to license or deny any field that could be mistakenly associated with its trademark, the university expanded its trademark from blue to non-green in 2010.  Boise State does not claim to own all colors, according to Bradlee Frazer, an intellectual property lawyer who works with the university. But he said the field’s fame transcends its hue — and for that reason a consumer could confuse any non-green field with Boise State’s.  Several trademark experts called that a stretch.  No institution has challenged Boise State’s trademark interpretation, but several experts said they believed that a school wanting a non-blue, non-green field would most likely succeed if it did. It is impractical to think that any momentary confusion would change purchasing decisions or sports allegiance, said Mark Lemley, a trademark expert and Stanford University professor.  “I see why they do it,” he said of Boise State defending its turf, “but it’s not a patent. Trademark law is designed to protect consumers from being confused. It seems unlikely that someone would be confused at all, and even if they are, it still seems ludicrous.”  In an email, Bickerton called that “an overly simplistic response based on a superficial review of a valid legal argument.”  “Initial interest confusion does not require actual confusion, merely that the mark captures the consumer’s initial attention,” she wrote. Articles on new colored fields, she added, usually refer to Boise State, “thus drawing an association.”  While the legality of the artificial turf trademark may be a matter of dispute, the motive for an increased focus on licensing is not: From the 2002-3 academic year to 2015-16, annual licensing revenue at Boise State has increased more than tenfold, to $750,000.  Still, Bickerton knows not everyone loves the blue. She sometimes reads the criticism on Twitter during games, but it no longer bothers her.  “Love it or hate it,” she said, “you know it’s Boise State.”  A version of this article appears in print on September 11, 2016, on page SP5 of the New York edition with the headline: A Paper Defense of the Home Turf. Order Reprints| Today's Paper|Subscribe
The university holds a trademark that covers not just blue football fields, but fields of all stripes — including stripes.