Ok, like you I don't know too mych. However, when I had a balcony I had a couple of dwarf conifers, you can get them in lovely colours. They will withstand cold weather.
If you go and look at a garden centre they will have plants outside in pots, these should be suitable for you as all the ones that don't like the cold will either not be about or be safely stored in doors. Always look at how big they will grow and how quickly. Some garden centres have topiary plants which have been cut to a shape which look quite decorative. I would suggest you look for hardy shrubs and conifers. Some shrubs produce lovely berrys etc in the winter for added colour. And if you don't want to be picking up leaves look for evergreens.