There have been a few sightings of different colours available for the ps vita as Omega said. Including the g4tv website, as well as the japan tokyo game show. http://www.g4tv.com/thefeed/blog/post/716523/custom-playstation-vita-colors-revealed-at-tokyo-game-show/
Agreed, it will be very similar to the release of the PSP I imagine.
I doubt we will get many differant colours over here. It only seems to be nintendo who care about giving you a variety, though anything other then black and white can seem very kiddy if done wrong. (The Pink DS lite for example, looks like a bad colour choice. The Blue 3DS on the other hand, actually looks quite nice)
Bear in mind, they announced loads of colours of Wii before launch and ended up only doing white for a few years and then eventually black, because Nintendo decided more colours would not increase sales significantly. Sony may release more colours of Vita, but probably not soon.