Apple on Tuesday fired off invitations to a September 10 event at which it is expected to spice up its iPhone line and unveil a low-priced version. In true Apple style, the invitations revealed little. The message \"This should brighten everyone\'s day\" was below the company logo on a page dotted with brightly colored circles. The design seemed to lend credence to unconfirmed reports that Apple plans to release iPhones in a rainbow of colors, including gold. The special event will take place at Apple\'s headquarters in the Silicon Valley city of Cupertino. Apple is rumored to be readying two new versions of its iPhone, with one a less expensive model to win over budget buyers in emerging markets such as China. Apple\'s move comes as pressure mounts from rivals such as Samsung that field Android-powered smartphones running the gamut of prices.