But as much I think about the colors of a fireplace, I can't help but think of the color 
blue (and 
white) a little bit more, maybe just
 light blue.
The song sounds so sad and (well...) blue to me, like the color of crying, desperation, longing and inklings of lonliness.
"I've been trying to do it right
I've been living a lonely life
...
I don't know where I belong
I don't know where I went wrong
...
I belong with you, you belong with me, you're my sweetheart"
 
It's like the person in the song is singing about losing someone near to them, but they're trying to be happy about it and remember the good times they shared, but at the same time, is begging her to return. 
He's lonely, he's trying to move on and just live, but he doesn't know where he belongs. All he knows is that he belongs with the person he lost.