The Blue Monster is a big blue beast who was an enemy in the Juniper Lee game: Monster Mayhem. It is light blue with yellow horns. In the Batoot episode, Not in My Backyard, one was shown dating a female pink monster at a restaurant with tea, but their tea cups broke from the Batoot's loud stomping sounds. In the episode, it is more dark blue with black horns.
The monster also appears in the online Juniper Lee game Monster Mayhem as one of the monsters the kids are turned into.