I chose the airbrush color Model Air of Vallejo and can only recommend this as well. It is reasonably priced and has a great quality. Important when choosing a color is the range of colors, offered by the manufacturer.
The Vallejo colors are actually made for military models, but they are just so good for Star Trek models, because there are many camouflage colors. This is great for the Klingon Romulan Cardassian... ships. As well, the selection of grays is good for the Starfleet ships.