The Princess phone was the first model designed from a marketing perspective instead of an engineering perspective. The Princess was also the first Western Electric phone to have a trademarked model name instead of just a model number. Model numbers are not as memorable as names, and numbers can't be trademarked. It's name was chosen from a list of 300 suggestions. The Princess also made history with an internal light bulb to act as a bedside night light and to aid dialing in the darkness.
The Princess went into production in 1959, and although radically different in appearance from previous models, the technology in it was the same.
It was initially available in any standard phone color except black, which was added in 1963. Legend has it that black was added when Jackie Kennedy wanted one.