During the early years of the Kaiju War, Romeo Blue becomes the second Jaeger deployed in combat when the Kaiju Hardship makes landfall after dark in an undisclosed city. At some point during the battle, the Kaiju grapples with the Jaeger in an attempt to tear off its Conn-Pod.
However, Romeo Blue is ultimately able to overpower Hardship, utilizing a chunk of beltway bridge as a melee weapon and consequently earning its first Kaiju kill. Shortly thereafter a parade is orchestrated in celebration of this victory, which is broadcast around the world.
Later, Romeo Blue was deployed in Seattle to prevent a Kaiju from destroying the city. The Jaeger is destroyed when the Kaiju tears off its arm and smashes through the Conn-Pod, killing the pilots in the process. The remains of the destroyed Jaeger were then taken to the Jaeger graveyard, Oblivion Bay.
Like most Mark-1 Jaegers, Romeo Blue is powered by a nuclear reactor. Its armament is primarily long range; including a Gatling Chest which allows Romeo Blue to attack a Kaiju from a distance. "Tracheal Break" is one of its signature moves. Romeo Blue is one of the slowest Jaegers ever made because of its immense weight, having one fifth of the speed of Striker Eureka.
Romeo Blue has a wide body and two small fins at the back that are similar to the T-16 Angel Wings on Striker Eureka. Its head is small and bears a crest at the top. The visor is thin and is symmetrical on either side of the head. Its hands are rounded with short fingers, relatively similar to Crimson Typhoon. The lower torso of Romeo Blue is quite thin before it gets wider for the hips and legs. A large and distinctive vertical fin-like structure protrudes from the center of the Jaeger's chest and was designed to protect the Conn-Pod from attack.
- The following is a roster of named Kaiju defeated by Romeo Blue, assisted or on its own.
- "Romeo Blue" is a stage name guitarist and singer Lenny Kravitz used during the 1980s.
- Romeo Blue's appearance in Pacific Rim is a cameo.
- Romeo Blue was originally designed as a tripedal (three-legged) Jaeger. Pacific Rim: Man, Machines & Monsters states that its body language was "Tripedal Sentry".
- According to Pacific Rim: Man, Machines & Monsters, pilots Bruce and Trevin's last names were "Jules" and "Mackenzie", suggesting the two were not related.
- Romeo Blue was launched after Brawler Yukon and Tacit Ronin, but before Horizon Brave and Coyote Tango.
- Romeo Blue appears in Pacific Rim: The Mobile Game and Pacific Rim: Breach Wars.
- Romeo Blue was included in the Series Five line of NECA's Pacific Rim action figures.