Sydney may have mourned the end of the rainbow on Oxford Street this week, but James Brechney was determined not to let it rain on his parade.

Armed with a bucket of chalk and a rebellious streak, the Surry Hills resident has sparked an urban protest movement that is bringing a splash of colour to the city's sober streets.

Mr Brechney, his sister Kelly and Wladi Dirksen, a German backpacker who is staying with them, channelled their inner children this week by chalking a huge rainbow outside their house on Commonwealth Lane.

Their DIY artwork was in protest at the state government's unpopular decision to rip up the colourful pedestrian crossing on Oxford Street, installed to mark 35 years of Sydney's Mardi Gras.