Synesthesia
When Mikasa sees red, the meanings whirl around like a thousand cicadas in her mind, swirling faster and faster until they become a muted hum that drown each other out in an effort to be the loudest. It is during this monotone that she can finally breathe and gain control of herself. If the buzzing is strong enough, it becomes nothing in her mind, like if you were to say the same word over and over again. The tuneless music is enough to prevent the monsters of her memories from clawing their way to her eyes and force her to relive moments that refuse to be forgotten or ignored.
Despite red being the color of the life that she spills on a daily basis, (whether it's another's or her own) the memories of knives and a childhood lost are brightened with a new expression of a dawning sun-a life started anew. A pair of green eyes that looked at her through swollen, tired lids, sometimes that darted to stare at the ground when her gaze would return too strong.
While red symbolized the innocence that was stolen and the hearts that ceased to beat, (One forced by her own hand) it also laced together a new future with the face of a savior sewn into its threads. Her savior was by no means merciful or gentle; he was often brash and filled with rage. His brow would come over those green orbs-so intensely for a child- and his teeth would clench so tight, Mikasa was sure they would damage themselves until they resembled the cracked edges of the home she had left behind, along with the bodies of her parents. Yet, there was a surprising attempt at gentleness when the boy wrapped that scratchy maroon scarf about her neck. He was not accustomed to giving soft touches or expressions of love; such was not in his nature. But when he made the effort to be certain of the orphaned girl's warmth, she found that perhaps red didn't have to taste like the bitterness of metal, or the pain of a parent's warmth abruptly stolen.
Suddenly, red smelled like the muffins Eren's mother had made that morning and it tasted of the sensation of belonging and purpose that was nursing the frayed edges where her childhood had once resided. True, the color would always be etched into her mind when she closed her eyes to rest; she would always see the stream of red that had poured from the knife encased in her father's beating chest. But it wasn't just the symbol of death now, it was entwined with the sensation of safety that the Jaeger's had provided for her when there was nowhere left to go.
All of these sensations and interpretations would be overwhelming to a human being, even one as gifted as Mikasa Ackerman. So she came to prefer the noncommittal hum that constantly fluttered in her mind, finding that it was much easier to think when in truth, she wasn't thinking at all.