Green (Normal Operations) The main engine core is running at 60% and the weapons are at cold status except for Phasers which are at warm status.
Yellow Alert (Cautious Operations) The main engine core is brought up to 100% and all weapons are placed on warm ready status except for Phasers which are brought to stand-by.
Red Alert (Alert Operations) The main engine core is brought up to 100%, shields are automatically raised and all weapons are brought to stand-by. The auxiliary control room is powered up in case it is needed. A level 3 diagnostic is run on all systems to make sure everything is running properly.
Blue Alert (Landing/Cloaking) The main engine core is reduced to 45% and weapons are at cold status. Hoverpads are engaged and main shuttle bay is brought to planet's atmosphere standard. Once the ship is grounded a ramp is extended from the shuttle bay for access. Depending on the planet's status, most crew is allowed to exit leaving only essential systems monitored such as Science, Security, CONN and Engineering.
External Support Mode (Docked at Starbase) Sometimes called Condition Blue, the engine core is dropped to 20% power nominal and the main power trunks are routed through the starbase's power system.
Grey Mode - Reduced Power Mode (Power is below 26% of normal) Main engine core is offline, weapons are brought offline. The reactors will try to regenerate as much power as possible and the bussard ramscoops are collecting hydrogen atoms. Non-essential systems are taken offline.
Stealth Mode (No subspace communications) Stealth mode (sometimes referred to as "Silent Running") is the complete absence of subspace communications, including intraship communications. The ship does not emit any type of unnecessary radiation signals and the warp core is boxed... while the ship systems run on the generators instead of the core. Similar to a 20th century WWII submarine after diving when they switch to batteries instead of the engine. Detection rate is less than 1%.