Purple
When Kairi first saw it happening, she thought it was a glitch.
The walls, the ground, her clothes – the same pulsing blue lines were everywhere, like the very heartbeat of the computer itself. But the moment she'd accidentally brushed against Sora, she could have sworn the place where her fingers had come into contact with his arm had briefly turned purple.
Huh, that's strange. Before coming inside the computer, which had been a trippy experience in and of itself, Sora had talked her ear off about everything she might possibly need to know about this place. One of the things he'd mentioned was that good programs were blue and bad programs were red.
Well, the good news was they hadn't run into any red yet. But where did that leave purple? He hadn't mentioned anything about purple. She was almost afraid to ask.
So she followed after him and Donald and Goofy instead, taking in the beautiful alien landscape around her. The pink canyons and lakes filled with glowing water looked like they belonged to another world, and in a way she supposed they did.
After a while, Donald and Goofy went to go try their hand at some of the racing games, leaving Sora and Kairi to themselves. Right before they left, though, Donald poked Sora, and the lines on Sora's arm were the same blue as ever.
Huh. Interesting.
She and Sora went exploring for several hours before deciding it was time for a break. She took off her socks and boots and dangled her feet into the water of a nearby pool, which Sora informed her was actually energy.
"From what Tron told me though, it's basically just water. Programs need it to live, and he says Users like us can drink it, too."
Curious, Kairi cupped her hand and scooped some of the silvery liquid into her palm. Lifting it to her lips, she poured it into her mouth and drank. It cooled her throat as it went down, and she felt her energy returning like she'd just eaten a meal.
"How's it taste?" Sora asked, sitting down beside her.
"Delicious. It restored my energy, too. Here, try some." She scooted over so he could have easier access to the pool, and her leg brushed up against his arm as he lay down on his stomach.
There it was again. The blue lines on their clothes turned purple.
So I wasn't imagining it. It really did happen.
Sora scooped some of the water into his mouth. "Woah, you're right. It tastes awesome. I feel better already." He took off his helmet and splashed some of the energy water on his hair and face.
"Sora, sit up for me, will you?" Kairi asked. She had a theory, and she wanted to test it out.
Curious, he tilted his head to one side but did as she asked.
"Okay," she said, "this is gonna seem weird, but bear with me. You know how our clothes have blue lines all over them?"
"Yeah?" he said, as if it was pretty obvious. Well, it was, but that wasn't the point.
"I'm gonna touch one of them and see what happens, okay?"
He raised an eyebrow. "Why?"
"You'll see." Chewing her lip, she tentatively reached towards his chest.
"Kairi?" he asked. The only colors here were varying shades of black, white, gray, and blue, and yet she could have sworn his face was turning red.
Oh. Had he expected her to touch his arm instead? He had sort of held it out, but her fingers were now inches from his chest instead.
Well, too late to change course. Her fingers connected with one of the lines on his chest. The glowing blue turned purple, and she traced a path across his breastplate. The purple followed her touch till all the lines on his chest were violet instead of blue, and the color change was likewise spreading up her arm.
"Do you see that?" she said, finally removing her hand and looking up into his eyes. He swallowed and nodded. It would seem he was incapable of speech at the moment.
"I had no idea you could do that," she said, tracing little loops of purple against the blue on his arm. "I thought the only colors here were red and blue."
"So… so did I," he finally managed. "Tron never said anything about purple."
"Purple? What's purple?" came Donald's voice.
"Donald, Goofy, watch this!" Kairi said. She was excited to share her discovery with them. How cool was it that she could make Sora turn purple?
Sora blanched. "Kairi wait, don't—"
Oops, too late. Her hand connected with his chest, making it change color all at once.
"Woah," Goofy said. "Hang on, Donald, why don't we try that?"
Donald quacked his agreement. He poked Goofy's arm, but nothing happened. The lines on his clothes were the same blue as ever.
"Here, why don't I try pokin' you instead?" Goofy suggested.
They got the same result. Blue.
"Kairi, do that again," Goofy said. Sora sighed but offered his arm to her, and she touched it lightly. Yup, purple.
"Huh, maybe it's somethin' only Kairi can do," Goofy said. She poked their arms when they offered, but sure enough, they stayed the same color.
They finally realized what was going on, and as they turned to Sora with the exact same look on their faces, his earlier protest suddenly made a lot more sense.
"Guess what, Sora?" Donald asked, a sly smile on his face.
Sora gritted his teeth. "What is it, Donald?"
Donald pointed dramatically at the purple lines and paused for full effect before saying, "You're turned on!"
He cackled at his own joke like it was the funniest thing ever. He thought it was so hilarious, in fact, that he collapsed into a pile on the ground and rolled around on the floor. Goofy likewise was smiling like he'd just won a lifetime's supply of sea-salt ice cream.
"Donald's right, a-hyuck. I always thought that phrase didn't make much sense, but now it kinda does." He paused and scratched his head. "Wonder if it came from this world."
Oh, they were never going to let Sora live this down. No wonder he hadn't wanted them to know. Right now he looked like he wanted to plunge into the energy pool and never come out.
After another round of teasing, Donald and Goofy went to go take a swim in the energy water, and it was just the two of them again.
"Sorry, I wasn't trying to give them more material to work with." She gave his hand a sympathetic squeeze, and purple shot all up and down both of their arms. He looked even more like he wanted to disappear into the ground at the sight of it.
"Thanks a lot," he muttered. "It's not like I can help it."
She giggled into her hand. "I know. It's kinda sweet, actually. Y'know, since it happens to both of us." She poked his chest and traced a path downwards, the purple following her finger wherever it went.
Sora's breathing was getting heavy, and she leaned in closer. "Hmmm, I wonder what it would take to make you turn completely purple," she whispered in his ear. "Think I could make it happen?"
He made a choked noise, and she grinned and winked. Oh, teasing him was fun. There was so many different ways to push his buttons.
She readjusted her weight and scooted closer. "Here, I think I'll try—"
"I've got a better idea," he said, his voice lower and gruffer than she was expecting. He put his arm around her waist and pulled her close. He had that look in his eyes and his breath was hot on her cheek and his mouth was right there, was he really going to—
Yes, yes he was. His lips brushed her cheek, and Kairi was pretty sure her entire body had just turned purple because Sora, competitive little sneak that he was, had downright cheated.
Kissing wasn't fair. It just wasn't. But she melted in his embrace all the same and enjoyed every moment of the kiss, even if it was just a peck on the cheek. When he leaned back, he had the most triumphant look in his eyes, smug and satisfied and elated all at the same time.
She caught a glimpse of her reflection in the energy water, and she was purple from head to toe. Oh, she wanted to slap him and kiss him at the same time. The stupid little cheater had just won and it wasn't even fair.
"Now who's turned on?" he said with the biggest, stupidest grin on his face, just to really drive the point home.
"You little sneak!" she shouted, even as she tried not to laugh. He'd already scrambled to his feet, knowing what was coming, and she jumped up after him. He tried to summon his Keyblade just a second too late. She got him with a nice Stop spell before he could, and he froze near the edge of the energy pool.
He was unable to move, but his eyes followed her as she circled around him. Oh, she was going to take her time and enjoy this.
"That was nice and all, but you're going to have to do better than that." She wrapped her arms around his shoulders, then stood on her tiptoes so she could whisper in his ear again. "I want a proper kiss next time."
Just like that, his hands were on her waist. "That can be arranged," he said, and before she could stop him, he hoisted her high up in the air, so high that she was practically flying.
"Sora!" she squealed, half indignant, half thrilled. The sound that came out of her mouth as he caught her in his arms was somewhere between a giggle and a yelp. He grinned and dipped her so low to the ground her helmet fell off and the tips of her hair dipped into the energy water.
"Y-You broke my Stop spell!" she sputtered, wobbling as he readjusted her weight till he was holding her bridal-style. "How? How did you do that so quickly?"
He paused, then gently set her back on the ground.
"Dunno. Guess I really wanted that kiss," he said, tracing a blue line on her hand and watching it turn purple.
She smiled. "Well, what are you waiting for?"
That. That was all it took. He brought her into his arms and kissed her nice and properly. So properly, in fact, that they lost their balance and fell into the energy pool just as things were getting good. Ah well. It was a pretty great kiss otherwise.
Purple had always been Kairi's favorite color, with its lilacs and violets and lavenders and plums. But she'd never realized how much more it could be. It was their color now, theirs to giggle at and joke about and reminisce over.
And sure enough, Sora would drop everything he was doing and smile at her whenever she said the word purple after that. The way she said it would tell him exactly what she was thinking and feeling, too, like their very own secret code.
The day he started doing it back was the day her heart felt so full it might burst. It was funny how just one word could contain an entire world's worth of meanings. How just one word told her everything he felt about her and conveyed everything she thought about him.
But it did, and that was why purple was not just her favorite color, it was the best color. It was the best color by far.
A/N: This story was inspired by one of the deleted scenes from the original Tron movie. It has this moment where the blue lines on Tron's suit turn purple when Yori touches him, as does her arm. It's a really cool piece of worldbuilding, and it's the only time this happens in the entire movie and shows that Tron and Yori's relationship is special.
Anyway, if you'd like to see it, the scene is on YouTube. As always, thank you for reading!