Blue

Blue can refer to the weapons: Or the headgear:

Or the clothing:
 * ❌, or Baby Jelly Shirt
 * ❌, or Dark Urban Gilet
 * ❌, or Firefin Sweat Navy
 * ❌, or Mountain Gilet
 * ❌, or Rainy Day Tee
 * ❌, or Sailor Stripe Tee
 * ❌, or Shirt and Tie
 * ❌, or Sky Blue Squideye
 * ❌, or Tricolour Rugby
 * ❌, or Vintage Check
 * ❌, or Rainy Day Tee
 * ❌, or Sailor Stripe Tee
 * ❌, or Shirt and Tie
 * ❌, or Sky Blue Squideye
 * ❌, or Tricolour Rugby
 * ❌, or Vintage Check
 * ❌, or Vintage Check
 * ❌, or Vintage Check

Or the shoes:
 * ❌, or Blue Biker Boots
 * ❌, or Blue Plimsolls
 * ❌, or Blue Biker Boots
 * ❌, or Blue Plimsolls
 * ❌, or Blue Plimsolls

Or the multiplayer stage Bluefin Depot

Or the Blue Team from the Splatoon manga.