Apple has silently overhauled the internal designs of the upcoming iPhone 5S and the tweaks would likely lead to the iOS 7 device being offered in multiple colour options on release date, a new report said.

The reworks inside the iPhone 5S guts, according to BGR News, were made to accommodate new handset components and features, chief of them is the sapphire-coated fingerprint sensor that serves two purposes - tougher mobile security and secured wireless payment processing via near-field communications (NFC).

Citing an unidentified source, BGR pointed to the following internal parts as the 'invisible' to the iPhone 5S: loud-speaker bracket, ear speaker bracket, vibrating motor assembly, Wi-Fi flex cable ribbon and SIM card tray.

The latter will reportedly come in different colours, supporting earlier rumours that Apple will retail its new flagship outside of the usual black and white choices.

While the leaks could not be independently verified, the iPhone parts shown were called 'plausible' by numerous blog reports, adding that the expected arrival of the revamped iOS 7, thereby spawning new features for the smartphone, indeed requires major adjustments inside.

This week, reports have suggested that Apple is ditching the physical Home button in favour a capacitive alternative. The switch was intended to provide more durability to iPhone 5S owners, made possible by the elimination of a moving part, which in turn greatly mitigates the wear-and-tear factor of the device.

At the same time, the new key will be coated with sapphire to make it scratch-resistant and beneath the same button, a fingerprint sensor chip will be embedded, which is designed to bolster the iPhone 5S' security features.

Analysts believe Apple is set to rollout the refreshed iPhone by September this year and it will be accompanied by the so-called budget iPhone, which represents the tech giant's entry into the mid-range smartphone market.

By June 2014, the company will likely release the phablet-size iPhone 6, which will usher Apple's entry to the increasingly lucrative hybrid smartphone arena, where device screen size ranges from 4.5-inch to 6-inch.