Green Bloon, alongside Swarm Green Bloon, are cheap, 1 delay Aggro Bloons that have much more health than Blue Bloons. They are best used early to kill the opponent alongside cards like Yellow Bloon or Blooming Bloon.
Greens are less flexible in Aggro than cheaper cards, due to its higher cost, however they're more tanky against low-damage attacks and have 1 delay. Greens are still often used in Aggro decks.
Greens are between the cost of Blues and Yellows, making them somewhat flexible between cheap for combos with Bloons like Bolstered Bloon and powerful enough to be used on their own.
Greens are good for Amelia Aggro. Its two charges and 2 Gold are just enough to afford Bloon Shield, which is good against chip damage.
If buffed by Zee Jay's Passive Enhancements, the Green will go over the threshold of Overload. It is good for Zee Jay aggro when combined with powerful Bloons such as Blooming Bloon.