Disclaimer: I don't own SPN.

So this is based off a Tumblr post I found on Facebook – I added it to the fic on AO3, where you can embed pics, if you want to see what it was. And this is for you, masterjediratgrl31, because you're the one who made me write it -_-

"I bet that I can guess your favourite colour," Cas challenged. Dean raised an eyebrow but didn't stop stroking his boyfriend's hair.

"Oh, yeah?" he said. That was going to be completely impossible, since he didn't have a favourite colour (though he was definitely partial to blue, especially the shade of blue that made up Cas' amazing eyes), but he wasn't going to tell Cas that. He wanted to see what Cas thought about him.

"Yeah." Cas wriggled around in Dean's arms so that he lay on his belly, smirking at the green-eyed man. "I'll even bet on it."

"What are you willing to offer? Your sweet ass?"

Cas rolled his eyes, smiling fondly.

"Not everything is about sex, Dean."

"It is when you're as handsome as you are." Dean shot Cas a wink and grinned triumphantly when the ex-angel's cheeks flushed.

"Stop teasing me," Cas grumbled. "I still may not understand humanity fully but I know that you are trying to – what is it? Turn my knobs."

Dean closed his eyes, biting his lip to try and stop himself from laughing.

"Push my buttons, Cas. If you're gonna use human slang, at least get it right."

Cas rolled his eyes again; an annoyingly endearing habit that he'd picked up from one of them (most likely Sam. That bitch always did love to roll his eyes at Dean like he was superior).

"Whatever. Take a guess, angel. You get it right first try, you can do whatever you want with me for a whole day."

Cas' eyes lit up with a predatory gleam.

"Does that mean that I can finally get you to take me on a date?"

Dean grimaced. Going on dates was not how he did things, much to Cas' chagrin when he found out. The ex-angel had been trying to get him to go on a date for a month now but Dean wasn't budging. What was the harm in agreeing? It wasn't like Cas knew that he didn't have a favourite colour.

"If you win. If I win, same deal. I can do whatever I want with you for a day."

"Deal!"

Cas heaved himself up into a sitting position. Dean made a noise of complaint, until Cas pulled him to sit up as well and then began to examine him with unblinking blue eyes. Dean squirmed under his intense gaze, until Cas finally hit him and told him to stop moving so much.

"Yellow!" Cas finally guessed. Dean was about ready to smugly tell Cas that he was wrong and that he couldn't stand yellow when he realised that Cas was looking at him expectantly with a huge, excited smile – in fact, the biggest smile he'd ever seen on the ex-angel's face. This really meant a lot to Cas, didn't it? And how would he react if Dean told him that he was wrong? Dean mentally sighed, already preparing himself for the date – but it would totally be worth it if Cas kept smiling like that.

"Dammit!" he said, heaving a huge, fake sigh. "Got it right first time, Cas. How'd you know?"

Cas actually laughed and surged forward to wrap Dean in a tight hug. A wide, unbidden grin slid across his face and all he could do was hug Cas back, breathing in his honey-scented shampoo and realising that he was so in love with Cas that he was screwed in every way possible. He'd do anything to make Cas smile and laugh like this again!

"I guess that means I owe you a date," he said. Cas drew back and kissed him hard in response.

"Don't worry, Dean. I know you well. There won't be any expensive restaurants and fancy clothing. I simply want your company."

True to his word, Cas' idea of a date was lunch at a nearby diner – not as high quality as all those fancy places out there but not a total dump like their usual stops either – and then pie for dessert, eaten in a park on a bench.

But Dean couldn't stop thinking about anything except for yellow. Ever since Cas' excitement over it yesterday, he found that it was utterly impossible to see the damn colour the same as he had before Cas' guess. It was freaking everywhere: the flowers dotting the grass, the leaves on the tree above them, the slide that kids were hurtling down with shrieks of laughter, the rooftop of the house nearby…it was everywhere and he couldn't get away with it now but he didn't care. All of it reminded him of Cas and his beautiful wide smile and how he'd do anything to make the ex-angel smile like that again. Hell, he'd freaking paint himself yellow and live in it if Cas would give him that big grin again.

Oh, yeah. Yellow was definitely his favourite colour.