Some people are born blind to colours, and there's nothing they can do about it.

John suspected that Sherlock was blind to sentiments instead.

As smart as he was, there were times when he was just as clueless as a child – he couldn't really understand people's motivations when it came to sentiments, and that made him vulnerable in ways nobody would expect.

That was one of the reasons why John kept sticking to his side, no matter how irritating his friend could be sometimes. Well, most of the times, actually.

He liked the thrill of danger, that was true; however, even that wouldn't be enough in the long run, if he didn't feel responsible for Sherlock as well.

Their friendship could be described as odd at the very best; in a way John had taken the place of the big brother that Sherlock hadn't really had, the one that Mycroft would never be.

In the end he simply had to accept the fact that he was sort of married to his friend, exactly like Sherlock was married to his job. They were indeed a couple, though not in any way people would understand.

He looked after Sherlock, and Sherlock was secretly grateful to him for that. John was the closest thing to a friend that Sherlock would ever have, and that worked for the two of them.

People could keep on talking as much as they liked, he'd stopped caring a long time ago.

As for Sherlock, he'd never cared about it in the first place.