There are 8 forms: Blue and Yellow both have electricity around them and you have to use the bow and arrow to kill them or the boomerang to stun them and stop the electricity, and there are also Green and Red which are non electric and are just plain annoying. The Dark ChuChus which are only seen in Wind Waker must have light reflected upon them in order for them to become attackable. There are also ChuChus that will wear a rock or a helmet for protection. These are colored red. There are Chuchus that have spikes that extend to protect themselves. There is even an Ice ChuChu which as its name implies attacks by freezing enemies.
In the Minish Cap there is a gigantic Green ChuChu who acts as a boss in the first temple Link goes to. However this ChuChu is not large but instead it appears to be due to the fact that Link is tiny in size.