Paintballs are not created equal
Paintballs come in an array of shapes, sizes, colors, less lethal, clear, powder, glow in the dark, rubber and yes.. scented! Scented? Did you just say scented?... Yes Real Action Paintball (Rap4) has different scented paintballs from apples to buck lure.
You can find wholesale paintballs just about anywhere, however saving a few dollars can mean the difference of making your shot hit the target.
You could use glow in the dark paintballs as tracers for a night game, fill about 20% of your hopper with a mix of glow in the dark paintballs for a realistic effect. Please also remember that for these balls to glow you will most likely need to install a light inside your hopper for the best effect.
But looking past the appearance you need a good paintball that will fit inside your barrel. A quick test to match a paintball with your barrel type is to put a ball into the barrel, if it rolls out then it's not a good fit. Blow on the barrel and see how much effort it takes to make the paintball shoot out the other end. If you face turns red you should try another paintball.
The key is to find a paintball that can fit snug inside your barrel without rolling out on it's own. If to much air escapes around the paintball while it is being propelled on it's way out will cause the ball to spin and lose accuracy. Too much resistance and the ball may break inside your barrel.
Rubber Training Balls
Black Rubber Training Balls
Fuzzy Target Balls
Buck Lure Paintballs
Clear Training Paintballs
Apple Scented Paintballs
Inert Powder Paintballs
Paint Mix (Mines, Grenades etc)
If you want to find bore sizes for paintballs and markers, just run some internet searches for "paintball bore size charts" to find out what equipment you have and how to match it.