There are a few ways that players can acquire free skins in Bloons TD. The first way is to simply complete the game on any difficulty setting. Upon completion, players will be rewarded with a random skin for one of the towers in the game. The second way to get free skins is to participate in community events that may occasionally be held by the developers. These events usually involve completing certain challenges or tasks within a set period of time and can often result in some rare or unique skins being awarded to participants. Finally, another way to get free skins is to purchase the game’s Season Pass which includes a number of different cosmetic items as well as other bonuses such as an exclusive tower skin and early access to new content.