I think there is a very good chance indeed that stones were painted or decorated in some way. Humanity has a long, long history of it.

You know all those greco-roman sculptures? They were all painted - bright colours, too. I find it inconceivable that carved stones, and rock art - especially those found in tombs were not painted too. Think for a moment of the Egyptian tombs and temples, pre-Columbian statuary with all its adornments of metal and jewels, native Australian rock paintings - all embellished with gorgeous colours and pulsating designs, symbols and totems.

The weather up here in these harsh wet northern climes would have meant that any stones outdoors here would have to have been painted afresh each season or according to whatever festivity was being celebrated. However, given that there are so many prehistoric monuments around the world that WE KNOW were painted, if ours here had not been, then WE would be a very strange exception indeed.