Black Widow's "Age of Ultron" suit completely goes against the character's nature and skill set. This is a hero who has spent years of her career operating in the shadows and using stealth to gain an advantage over her targets. Fans have been talking about the bizarre wardrobe choice for quite some time, with one Science Fiction & Fantasy Stack Exchange thread dating back to 2015. Fan Petersaber asked, "Why would someone who's focused on stealth have glowing stripes on their uniform?" It's a fair question.
Given her talent for stealth operations, it seems bizarre that she'd let Stark — or SHIELD — outfit her suit with blue electric cables that power up her gauntlets. Yes, the practical nature of the electric piping makes sense, but it's not exactly subtle for someone whose skills typically rely on sneaking around. The bright-blue electric cables are a beacon against her black suit.
On the other hand, there's an argument to be made that Natasha becomes a very public figure in the years since the Battle of New York in "The Avengers" as well as the Battle at the Triskelion in "The Winter Soldier." She even testifies before Congress after Hydra is discovered inside SHIELD. With that in mind, it's possible Natasha went along with the idea since she no longer works as a secret agent and instead operates as a fully fledged superhero. Either way, it's clear she tries to get back to what she does best when she goes on the run in her own solo movie, "Black Widow."
