WARNING: The following article contains spoilers for Daredevil #598 by Charles Soule, Ron Garney and Matt Milla, in stores now.
It's never been easy for Daredevil.
Having made it possible in the "Supreme" arc for costumed heroes to testify in court for criminal cases without needing to reveal their secret identities, Matt Murdock soon found that victory undermined by the revelation that his longtime enemy Wilson Fisk, the Kingpin, became Mayor of New York. What's more, his victory in the election came with little hesitation from the New York citizens, all of them eager for someone to deal with the chaos the city goes through on a near-daily basis.
With the city in the palm of his hand, it didn't take long for Fisk to put a bounty on Daredevil's head just as soon as he set the hero up to look like a villain in the eyes of the public. Ever the optimist, the only way for Matt to make anything good come of this mayoral change was becoming the deputy mayor. At the very least, he reasoned, he can use his super hearing to eavesdrop on the mysterious Sarnos Project that the new mayor is hatching up. In Daredevil #598, Matt hears some truly awful news -- and that means calling in an old "friend" to help him deal with his newest problem.
The third arc of Charles Soule's Daredevil run, titled "Dark Art," saw Matt go up against a vicious Inhuman serial killer named Muse who created extravagant paintings using blood. Daredevil and his apprentice Blindspot were able to stop him, but not before the killer took Blindspot's eyes from him. Since being in Inhuman prison, Muse has been content with living out the rest of his life behind bars and painting with the supplies presented to him. But after seeing New York police go on a manhunt for Daredevil and hearing that Fisk has declared superheroes illegal, Muse decided to break out and start painting. Only this time around, he's painting superheroes on buildings--namely, putting them in a positive light and putting uplifting messages next to them for Big Apple citizens to stop and gawk at.
Not wanting citizens to feel sympathetic for the people he just outlawed, Fisk authorizes local law enforcement to do whatever they can to bring Muse to justice. And since that led to lives being lost last time around, Matt decides to suit up and deal with Muse and follow up on the Sarnos lead. But instead of going around in the red suit again, he dons the black and red costume that he began with since Soule took over writing duties.
Though Matt was still in the black outfit during most of the current Defenders book, he truly abandoned it in the final pages of "Supreme." With his victory at the Supreme Court, Matt went back to the classic red, declaring that he realized he needed both his lawyer and hero identities and finally at peace with himself.
Through his narration, Matt makes it clear that he's donning the black and red again for practical purposes, not aesthetic; the costume allows him to blend in with the New York nightly backdrop easier, and helps hide him anyone looking to collect that bounty off his back. With Muse's involvement in the "Mayor Fisk" arc, it also allows for things to come full circle for Soule and artist Ron Garney, who illustrated "Dark Art," which also featured Matt in the black and red costume.
In Matt's own words, the reason he chose to be in black was meant to symbolize his Daredevil persona having turned into a warrior following the world ceasing to remember his double life. It's Daredevil the warrior who trained Blindspot, the warrior who waged a four-person war alongside the other Defenders against Diamondback, the warrior who fights for everyone else to see the perfect world that he never will. For Matt to go back to this costume against both Muse and Fisk makes it clear what needs to be done to protect Hell's Kitchen.
The battle for New York going on in "Mayor Fisk" isn't one that can be won with legal acumen or appealing to the soul of a friend--it can only be won by Matt fighting with everything he has. It's a battle that can only be won... by a warrior.