He sees the world in pictures.
He knows the others see the world in motion, constantly moving, bustling, busy. But he chooses to pause for moments. It's why he picks up a camera. Because others can finally see what he means. The can stop, for that one split second, and everything is perfect, preserved forever. And sometimes they would go back to that still and wonder why they cannot walk back to where they were until they realise they can.
There is something beautiful about that glimmer in their eyes when they look at a fond memory or a loved one. He lives for that beauty. it fills him with a wonder of his own, because he cannot understand them, sometimes. He doesn't feel the same way they do. He has never felt anything close to that nostalgia, that deep connection they form with those moments. For him, life is just like an album. Like one of those photograph reels that the muggles so treasure. He lives it for the brief second that encompasses a momentary stillness, and then moves on, having catalogued it away, sometimes in his mind, and often in his camera, if he is lucky.
At least, until the day when he realises that he is going to die. It is not an easy realisation, and he does not have enough time to slowly make his peace with it. it hits him out of the blue, literally, for the spell thrown at him is not from the wand of the person he was duelling. But wars are not fair, he knows. And it was foolish of him to assume they would be, after all. So he has a few seconds, the moments between the painful impact of the spell and his collapsing to the ground. the moments where the world seems to be a blur, a whirlwind.
As he lays dying, Colin wishes that time, as it so often had before through his pictures, would stop again for him, one last time.