It was the light. The glow transfixed him. He couldn't help it. Even in the middle of battles he'd find himself admiring it with something close to awe.
But, it was when they were off duty, when Tony would round a corner and catch him off guard with the radiating blue, that Steve would stare.
He couldn't pull his gaze away.
He was obsessed.
Steve only realized it when his sky blue and turquoise pencils were too small to hold, when he'd gone from drawing Tony to just the reactor to just filling pages in his sketch books with the color.
Page after page after page of the mesmerizing glow.
It happened all too suddenly, just one day, just a normal day. Steve was in the kitchen making toast. Then Tony was brushing past him with a mumbled "Morning" and Steve was turning to reply before he could stop himself and Tony was stretching up, shirtless, grabbing cereal from a top shelf and the light and Tony didn't even notice Steve still, staring, and then Steve's brushing his fingertips over the reactor and the light, the light, blue.
Tony stops breathing for half a second, but he doesn't move even as he remembers what lungs are.
Steve looks transfixed. They're both facing the cabinets so it's an awkward angle but Steve's got his palm pressed over the arc reactor, watching as blue spills between his fingers.
Then the moment's gone. Steve snaps back to reality, snatching his hand back as horror flickers across his face. Back peddling, the blonde puts his hands up, fingers spread, "Oh, God, Tony, I'm so sorry. I- I don't- Sorry, sorry. I didn't mean to- to, no, sorry. I-"
He's rigid, eyes wide in panic, as he finally looks at Tony, sees him. He's relaxed, but drawn into himself, confusion etching lines into his forehead.
"Steve. I'm not angry, but, uh, what was that all about?"
"I- I, uh. Look, I didn't... It's just I- I can't stop- I-."
"Woah," Tony breathes, with an amused twitch of his lips, hands raising to try to calm him down a bit, "Cap, you didn't kill me, no major social transgressions have been crossed. It's good, really. Just, you okay?"
That catches him off guard, and he's stunned, mouth agape, hands still up as he stares at Tony.
Is he okay? Is he okay?
"No! Shit, Tony, I'm obsessed!"
And then he's ripping open his sketchbooks, shoving drawing after turquoise drawing into Tony's shocked hands.
Tony flips through them once, twice, three times before he looks up, surprise fluttering across his face in a way that makes Steve's fingers itch for a pencil.
"Um, well, this is flattering..."
Steve, all big and tall and muscles, is trying his best to hunch, to take up as little space as possible, head bowed, eyes focusing on the floor.
"So, uh, you...like the arc reactor?"
He's worrying his hands when Tony looks up again from another flip through the drawings.
"I-I-I'm sorry. It's- I- It's the light, the blue, the- I-"
"Steve. Woah. I'm not upset or anything. Just slow down."
For a while he's just standing there, staring, tracing the shadows wavering over Tony's chest. He's beautiful.
"You're beautiful. The light, the angles, the everything, everything."
Tony freezes, gawking at the blue eyes that don't glance away, don't flinch, just watch him like all Steve had said was just fact.
"Uh. Okay," Tony flounders, running a hand through his hair, "So. Generally you're supposed to take me out to dinner before you say that, but, hey, we can switch the order, no problem."
And suddenly it just clicks, Steve gets it. Love's a complicated thing. No wonder he hadn't figured it out yet.
His hands were on Tony before he'd stopped chuckling at his own joke, grasping, holding, smothering the breath from his lips.
Tony leans back against the counter, Steve towering over him, panting, "Well, okay. Uh, yeah, 21st century, who cares about the order of things?"
This time he kisses Steve and by the way Steve's knees buckle Tony figures they definitely aren't going out for dinner tonight.