Actually in the original series gold was the colour that denoted a command speciality and red denoted the operations side of the ship (security, engineering etc) As of TNG the red and gold swapped over and cryptic have changed things again slightly in the game as red is now tactical; not command and gold is restricted to engineering
To really say that a color denotes position or career isn't accurate. For instance, Worf has wron 3 different uniforms between TNG and DS9. In TNG he wore both the Yellow/Gold and the Red. In DS9 and First Contact he wore the Grey shoulders, black torso uniform with the red undershirt.
Gordi was the same way, he worn both red and yellow uniforms. The only uniform that seems to denote career is Blue, which is Medical.
But also, Gordi first started on the Bridge, not as a Engineer, so one could say the Red is Operations. Operations could encompess the Commmanding Officer and Number One. Therefore, there wouldn't be a command color. So operations would be red, science would be blue, and yellow/gold would be engineering...in the TNG universe. In STO, the operations part of the ship would be what doesn't have a color, unless you use TNG color schemes, in which case Tactical would be red, as it is an operations position. But again you could argue the yellow/gold is tactical, as both Tasha Yarr and Worf both wore yellow/gold uniforms at the tactical position. Work wore the red uniform as a Helmsman as did Gordi.
So really color is all screwie and Cryptic just made it more so that way...:p