Last year a group led by Dutch performance artist lepe B. T. Rubingh cycled to an intersection in Berlin and dumped 500 litres of different coloured paint onto the road, effectively turning the street into a giant canvas, with cars acting as paintbrushes. The piece of guerilla street art was named "Painting Reality" and, in case you're worried about the after effects, all the paint used was water-based and was completely environmentally friendly.