BYU's royal blue was ICONIC in college football. Like Tennessee's orange, or Penn State's black & white. It "branded" BYU when people would tune in to the games. It looked fabulous on TV.
I am of the camp that BYU "sold out" when they decided to rip-off USU's Navy Blue (and yeah, yeah....I know ALL about how BYU wore navy back in like 1922 before TV and when players could fold-up their leather helmets) just because they wanted to sell more gear.
Bronco is firmly on record as being PRO royal blue and would make the permanent change BACK if he could.