Disclaimer: I don't own FMA.
A/N: I really don't know where the idea for this came from, but I went along with it, and I'm rather pleased with the result. Spoilers for chapters 39-101. Please review after reading.
The Color Red
Red is the color of the ink permanently etched into the smooth, white skin on her back, forming the intricate tattoo containing the secret of flame alchemy. It was a secret that frightened her, but she agreed to protect it nonetheless because she knew how important it was to her father.
Red is the color that tinted her cheeks ever so slightly when she exposed her back to her father's apprentice. She chose to reveal the tattoo to him because she believed without a shadow of a doubt, that he was trustworthy and would use the secret of her father's alchemy the way in which he intended it to be used.
Red is the color of his anger upon seeing the tattoo for the first time. He was furious that his teacher had done such a despicable thing to his only daughter. He couldn't even begin to imagine the pain she was forced to endure for the sake of protecting her father's beloved research. From that moment on he completely lost all respect that he had for his former teacher.
Red is the color of the flames that leap forth whenever he snaps his fingers. He had vowed to use the power so graciously bestowed upon him for the good of the people, but instead he used it in the government's war against Ishbal where countless people suffered agonizing deaths at his hands.
Red is the color of her eyes, bloodshot as the result of uncontrollable tears of despair when Lust claimed that he was dead. She'd given up on living and welcomed death because she didn't know how to live without him. He'd never before seen her so defeated, so entirely overcome with hopelessness.
Red is the color of the liquid that flowed swiftly from the gash across her throat as she futilely attempted to staunch the bleeding with her hand. There was nothing he could do while he watched in horror as she lay there dying, gasping for air and covered in her own blood. He never felt so useless as he did at that very moment.
Red is the color he despises the most because it reminds him of how close he came to losing her. Life without her would've been unbearable, and he was glad that he didn't have to find out just exactly how unbearable it could've been.
A/N: Yes, I know that Roy lost his eyesight in chapter 102 and thus can't see colors, but I'm disregarding that fact for this purposes of this fic.