The Double Blue Bloon is a Basic Blooncard in Bloons Card Storm. It deals double the damage if it hits the opponent's Hero, or damage equivalent with its health if the hero has Hero Protection active.
Double Blue does not possess many standout qualities. Most combos involving Double Bloons are more efficient with other types, and an unbuffed Double Blue does less damage than a normal Yellow Bloon, while effectively taking twice the damage as a normal bloon would.
For combo decks utilizing Quick Ready, Double Yellow Bloon possesses 50 more base health for the same delay and 2 gold more.
For Amelia Double Bloon strategies, two Double Red Bloons or one Double Green Bloon are less awkward for unlocking her Bloon Shield.
One possible advantage of a Double Blue is surviving against two Dart Monkey Twins and following up with Fortify. Because Double Greens and Double Yellows are easier to afford, this specific strategy only stands out on exactly Round 2 for both players.