Hoping to take another big bite out of the smartphone market, Apple on Tuesday unveiled its next-generation iPhone 5S, a new iPhone 5C in several colors starting at $99 and the latest version of its new iOS 7 operating system.

Apple marketing chief Phil Schiller showed green, white, blue, pink, and yellow iPhone 5C models at its Cupertino headquarters. The new phone casings are made of a polycarbonate translucent plastic.

The new 5C models will run $99 for a 16GB version and $199 for a 32GB model with a wireless service contract. It will be powered by Apple's A6 processor and sport an 8 megapixel camera. The 5C will run on 4G LTE networks.

Apple's dual phone attack will allow it to "serve even more customers," said Schiller on stage.

Schiller also took the wraps off Apple's iPhone 5S, calling it the new "gold standard" in phones. Apple's latest will be powered by a new A7 chip and come in a new a gold option in addition to black and silver. Apple's marketing chief says the processor is twice as fast as its predecessor.

Also new: iPhone 5S has a motion chip, called M7, which will send data from sensors to apps, which could mark its first step to wearable computing.

This fall is shaping up as a crucial season for smartphone makers. Apple is up against top Android phones from Samsung, HTC, Sony and LG, not to mention the new Moto X from Google's Motorola unit and Nokia's Lumia 1020 Windows Phone.

Phones in distinctive colors and styles are a big part of the competitive push this year. Moto X buyers on AT&T now can customize the look of the handset via the Moto Maker feature, and HTC just rolled out a metallic blue HTC One that is available exclusively at Best Buy.

Apple will reach its 700 millionth shipment of iOS by next month. Google recently passed its 1 billion Android activations.

ID=2794251With its one-time iron-clad grip on the the smartphone market under pressure, Apple is banking on a new hit. Its market share fell again in the second quarter -- to 14.2%, from 18.8% the year before, according to a recent report from research Gartner.

Apple sold more phones in the quarter — 31.9 million, up from 28.9 million a year ago -- but there's a huge gap between Apple and No. 1 ranked Samsung, which sold 71.4 million smartphones, up from 45.6 million.

Apple also took the final wraps off its latest version of iOS 7, to be released Sept. 18. The new operating system takes a stripped-down approach to the look and feel of the software. The new iOS 7 gives recommendations for commute planning much in the way Google Now does.

Also, iWorks will become a free app available on new iOS devices, offering creation of documents, spreadsheets and presentations.

Siri now comes in male and female voice options. The voice assistant has added new features such as the ability to return Tweets among queries.