Blue alert
Blue alert (also code blue or condition blue) was an alert signal status on Starfleet vessels and outposts which was called for in exceptional situations, including, but not limited to, environmental hazards to the crew, main power failure, docking and separation maneuvers, and landing protocols, for ships with the capability.

The bridge lighting on the refitted  turned blue when it prepared to enter the Earth Spacedock in 2285. ()

The alert for starships on auxiliary power in 2287 was a blue status screen, along with the main lighting on the bridge switching to blue. ()

In 2367, the event of an imminent environmental systems failure or disruption resulted in blue alert being called in the affected areas in order to help affected personnel escape or safeguard their lives. In such a case, the Captain and first officer were each responsible for directing any crew present into the officers' designated turbolift, waiting by the door as the crew quickly filed in. Only after did the captain ensure that the first officer's turbolift was entered lastly by the XO, did the captain then enter their own turbolift, and was thus the last officer off the bridge. ()

The  went to blue alert when engaging its Romulan cloaking device in 2371. ()

On a vessel with landing capabilities, such as the , blue alert was called as an indication that the ship was preparing either to land or to take off; the crew would then need to report to code blue stations, in order to aid in the landing/liftoff procedures. () Blue alert was the minimum required ship status for landing an Intrepid-class starship, as the  did make a landing while at red alert without switching to blue alert status. () 

Blue alert was also used when a  starship activated its multi-vector assault mode. ()

de:Blauer Alarm
ja:特別配置警報
Alerts