What do the different colors of uniform signify, and what are all the rankings? When Crusher goes from half ensign to full, what does this signify? What are the order of ranks on the deck?
ranks are easy. Starfleet uses US Naval ranks. btw, there is no half-ensign. that was merely a show plot device to get Crusher in a uniform on the bridge to be part of the action of the show. the color of the uniform designates what career you have. Red is for command, gold for engineering, blue for medical other support services, IIRC off the top of my head.
On Enterprise colors follow the TOS scheme, command and flight control (helm) officers wear gold piping, engineering and security officers have red piping, and science, medical and communication officers have blue piping. On the other Trek shows (TNG, DS9, Voyager): Red is command, Gold is Engineering, Security, and Operations, Blue is Medical and Science. Ranks are the same as in the US Navy. W. Crusher was an acting-ensign (which was merely a title as he held no true rank) until granted field promotion to full ensign by Cptn. Picard.
