Somebody's Washing (or Flags?)

I spotted these coloured rectangle things today whilst I was walking through the park in Wimbledon. I quickly whipped out my camera to capture images of them - I didn't care if I looked weird or like some kind of stalker, as I was literally across the road from my art college so passers-by would (hopefully) just assume that I'm an art student and therefore have an automatic license to randomly photograph things in public :)