Plant it to grow Blueberry. Careful with these, they'll stain! Throw it at a player to turn him blue for an hour.
Blueberry Seed price in Growtopia: sells for about 10/WL (median of 49 offers from community Discords, past 30 days). Live price chart and the latest buy and sell offers.
Recently sold at: SIMALA, IMUPMALL, WOXB, LUMSI, EEPSON