Hong Kong: As public sentiment turns sharply against the Hong Kong police and their attempts to quell the city's swelling pro-democracy protests, wave after wave of supporters arrived in the heart of Hong Kong prepared for a hostile reception.

Aware that riot police had been firing volleys of tear-gas into the crowds, they used umbrellas as shields, wore surgical masks over their noses and cling wrap around their eyes, and raised their arms in the air in the defiant style of the protests in Ferguson, Missouri.

The striking images splashed across front pages here, of colourful umbrellas being rained on with tear-gas, have already spawned a new name for the protests on social media: the "umbrella revolution".

But as protesters call for the resignation of Hong Kong chief executive Leung Chun-ying, and openly express their disdain for China's ruling Communist Party, it is the references to potential colour revolutions – a term applied broadly to civil movements aimed at overthrowing governments seen as authoritarian – that prompt fears about what lengths Beijing will take to end what has been a gravely sensitive turn of events.