generally on a drum kit you will have a hi-hat cymbal (represented by yellow), a ride cymbal (represented by blue) and at least one crash cymbal (represented by green).
The advantage of having 3 cymbals on your IONs is that you can play hi-hat crash and ride notes on the correct cymbal rather than having to hit a pad for one cymbal. Plus its way more fun
I have 4 cymbals (2 green crash cymbals. one on the left one on the right) and i want another one for when you have to hit a green and yellow crash at the same time but sadly there isnt enough room on the rack.