How To Get Blue Onion in Pikmin 4
Throw 30 Ice Pikmin into the small pond to freeze it completely. Use any color of Pikmin to build a wall beside the pond to create a path. Depending on how many Flarlic you collected in Step 2, your Pikmin may need to make multiple trips.
Commence Your Blue Onion Rescue Mission Blue Pikmin Sun Speckled Terrace Blue Onion Save Russ Last Frost Cavern
Source: techstory.in