Anything I can spray on patio to stop it going green?

There is a product on the market called Armillatox an excellent product .It is a soap based outdoor cleaner and though it isn't cheap it will give you satisfaction.A 500ml bottle will dilute for use at the rate of 100 to1 and the contents will cover 50 square metres.Ther's no rubbing , no scrubbing , ,just wet it and forget it and the green will disapear.