Q had...a lot of clothes. And if asked, Bond would freely admit that they weren't the first thing he noticed. To be honest, Q's wardrobe choices probably weren't even on the list of things that attracted the agent to his superior.
Well. Not at first.
After months of spending time together, and of Bond turning up in Q's flat so often they just admitted to living together, James finally started to notice. His memories aided his discovery. Q had a lot of clothes, yes; but he had the correct clothes for every occasion.
Work was work. Q dressed smartly, but sensibly. His tie was easily tucked away, sleeves quickly rolled up. Cardigans and trousers were his trademark look, and it was accepted by the whole of Q-Branch that their Quartermaster dressed like a naive Uni student on his way to his first interview. (Though admittedly, Q's budget for clothing was rather larger than that of a University student.) Initially, in Bond's mind, Q's 'uniform,' was only interesting in that it was hiding everything he truly wanted. The cardigans draped just too loosely to reveal how toned Q may or may not be, the trousers not quite fitted enough to hug the slim man's arse. Q's work clothes frustrated Bond, until the day he found them useful, and pulled his quartermaster in by the tie for an exploratory kiss.
Then there was Q in a suit. A jet black, finely tailored, classically styled suit. That outfit was James' favourite, for all of a week. The first time James had witnessed the mouth-watering sight was their first date. After months of Bond flirting, teasing, and almost outright begging Q had allowed James to make reservations. He'd been a constant presence in Q-Branch for the last week, until an exasperated Quartermaster agreed. "One dinner, 007. And not out of choice, I've just realised that it may be beneficial to negotiate with this particular terrorist, for the good of my department."
James had taken the opportunity gladly. He'd reserved a table at an upmarket restaurant, determined to impress the younger man. And then he'd disappeared for the rest of the week, apart from one simple text to Q. 'Dress smart. I'll pick you up at 20:00. James.' He hadn't realised that 'smart' would constitute a suit with a price tag to rival the agent's own. His eyes didn't leave Q the whole night. Bond found himself unable to ignore the way the white shirt complimented Q's pale skin, while the black tie contrasted it. And when he noticed, as the brunette laughed and sipped his wine, that Q's cufflinks were the exact shade of green that his eyes were...well. James was lost. He set his mind on taking Q home, to his bed, and then taking him apart completely.
Q's resistance lasted a week. Honourable, really, and a new longest record for 007.
The morning after that night, James discovered another outfit of Q's which he was rather fond of. They'd gone back to the agent's flat after their second date- "I really don't know why I'm accepting, Bond. I'm sure I said only one dinner."- and so James woke expecting a warm, long limbed body to be next to him. Perhaps another round, or at least a chance to touch again, map his lover's body in a calmer way than the previous night. "Q?", he'd mumbled. And in wandered the man. Gangly, pale legs stretched out endlessly from an open navy blue shirt. The undone sleeves covered dexterous fingers, and the dark material framed the pale chest and rosy nipples. Bond noted with satisfaction the slight finger marks on Q's hips, where his boxers weren't quite pulled up. "Done looking?", asked Q with a small smirk. "Mm. Is that mine?", James replied. "Well observed. Didn't think you'd mind me borrowing it.", came Q's answer, as he climbed back under the sheets and into James' lap. The conversation was finished, after that. The shirt stayed though.
Finally, a weekend arrived where both of the men were on leave. With promises from Moneypenny that they wouldn't be called into MI6 "unless something really bad happens, like the PM getting abducted. Again.", Q had made plans for a casual date. A trip to the cinema, nothing more. And Bond agreed at once. After months of formal dinners and parties, stolen moments in Q-Branch, and rushed nights and mornings together, something relaxed would be...pleasant.
This time, Q picked James up. The younger man was dressed in casual weekend clothes, and in the few seconds before James had him up against a wall, they both realised it was the first time the agent had seen his Quartermaster like that. Black skinny jeans clung to his legs, tight enough that Bond thought he must have been sewn into them. There were scruffy Converse on his feet, and he wore a plain white t-shirt and black jacket, zipped part way up. "You look like a fucking kid.", he growled into Q's ear, hands grabbing at the slim man's arse, unable to resist due to the tight denim highlighting it so promisingly. Q just smirked, muttering in reply, "Maybe it's just because you're so old, and don't pay attention to popular fashion." That riled Bond up even more, and he leaned in for a biting, bruising kiss.
Hours later, when Q had come twice (once, embarrassingly, in his jeans, due to the fact that James almost didn't let him take them off at all), Bond pulled him close. "That is my favourite outfit of yours.", he murmured, eyes darting to the jeans which had been thrown to the ground. "You said that about the suit, too. And your shirt.", Q laughed in reply.
Unsurprisingly, James was the one most likely to suggest more casual dates, after that.