The short answer is because the school could do it.
The idea was the brainchild of Gene Bleymaier, who has been the Broncos athletic director for 26 years.
"I guess that I'm the type of person that when I paint my house I paint it a different color so the neighbors notice you did something," Bleymaier said as Boise State celebrated its 20th year of playing on the blue turf in 2006.
Bleymaier came up with the idea in January 1986 when Boise State was scheduled to replace its previous turf. He got school president John Keiser to agree, thinking the plan would propel Boise State into the national spotlight for recruiting and give it a home-field advantage.
Both have come to pass as Boise State is a regular in the top 25 and famously defeated Oklahoma in the 2007 Fiesta Bowl.
The Broncos are on their third blue turf since the original dye went on to the carpet in 1986.
Two major myths propagated from the installation.
The NCAA has not banned other schools from going to alternate colored fields. Division II New Haven installed blue turf for its return to football this season after a six-year absence.
The blue turf is also not mistaken by birds as a body of water, as some believe.