in person, it isn't that bright nor green as the pictures... take note in photography, the camera somehows captures it's strong greenish tint, whereas in real life it's more whitish, and only if the aurora is strong, then you may see a little of green. If lucky, there may be hints of reddish hues as well. As for brightness, it will be brighter in photos as we tend to use longer shutter speeds in order to 'exaggerate' the brightness. 

the plus to see it in real life is it's magnitude as it may span across the sky above you, and of course you will see it 'dancing' around, changing patterns slowly.

You must go up to Tromso... Internal budget flight from Oslo to trmoso is possible... But you must research first if it's a good time as alot of factors t consider in order to see the nrthen lights....not cloudy, aurora activity forecast, etc...