Paint tubs at Swaffham wind turbine

We stopped off to look at the huge and eerily silent wind turbine at Swaffham this afternoon. In the grounds of the (closed) visitor centre, was this strange and unfathomable array. From a distance it looked like tubs of paint, but it turned out to be tubs that had been partly painted inside. Couldn't work it out at all, but I thought they looked sensational.