Tim Cook's departure as Apple CEO marks the end of an era defined by navy polos and dark jeans. The outgoing chief executive transformed Apple from a $350 billion company into a $4 trillion behemoth during his nearly 15-year tenure. His deliberate "tech uniform" became as recognizable as it was unassuming.

In contrast to Steve Jobs' Issey Miyake turtlenecks and futurist wire frames, Mr. Cook's look was purposefully bland. That blankness proved strategic — it allowed him to navigate between vastly different worlds: presenting a plaque to President Trump at the White House, attending the Oscars when Apple's "Coda" won best picture, or showing up at Coachella.

The Alabama native wore Zegna's roughly $1,200 "Triple Stitch" slip-on sneakers and Nikes, sitting on Nike's board since 2005. Critics note Apple's best-selling products riff on Jobs' ideas, but Cook executed ruthlessly — closing the Beats acquisition from Dr. Dre and launching Apple TV+. A deeply private person who came out as gay in 2014, Cook played the square while courting cool. It worked.