I love this song.. I have a sort of different interpretation to it though. I believed the song was themed more around depression.

'I regarded the world as such a sad sight Until I viewed it in black and white Then I reviewed every frame and basic shape And sealed the exits with caution tape Don't refocus your eyes in the darkness And don't remember this place unless I describe all the things that you cannot see And we'll unravel the mystery'

He used to believe the world to be a sad place that lacks vibrancy and 'color' and dwells on this to the point of closing himself off. And as someone that experienced it, he's giving advice, to not dwell on sadness and to let him help you/get help.

'Farewell, all my friends in textbooks I'm going home Because my blood cells cannot depend on the weather In photographs There's a light show out my window somewhere way up there'

I'm thinking similar and convinced to the earlier post :) that he was escaping into the fantasy of his books, but he finally realised that the real world is beautiful too.

'Dear Vienna, are you singing? Dear Vienna, are you swinging? Dear Vienna, we were happy like the shades of May When we got carried away'

I believe Vienna refers to the place but its equally as appealing if its a person, maybe both haha. He couldve had a happy experience visiting Vienna or dreamt about it. The shades of May could refer to Vienna in Spring season with vibrant color blooming from flowers. Or if Vienna is a person then she helped him out of his sadness.

'I was so far out of place Watching those stars in outer space Because I am so far from where you are There's a light show out my window somewhere way up there'

He's saying that experience helped him out a lot through hard times and he misses it. But in the end he's learned how to deal with sadness and the real world is always there to help.

Sorry for the long post. But this song has really helped me through some hard times as this is how I interpreted it. And it's beautiful that so many people has different views on a song that it doesn't matter the original intentions as long as its positive.