Unless the brick's natural color is really ugly and doesn't match anything, I would give hard and serious thought to painting them, as once painted it will be extremely difficult to strip them back to their original state.
To get the black soot color off, you will need to clean with a brick cleaner that contains both Muriatic Acid and a detergent. These agents are available from masonry shops and are usually effective, although you must be careful with them.
If you elect to go forward and paint them, you will need to prime with a masonry primer....usually oil based. This will serve to seal the bricks while providing a firm base to hold your final paint coat.