Joscha Bach says observables are ways in which reality changes.

“They are ways in which reality changes. So basically, to a functionalist, an object is not some kind of hidden essence that reveals itself to you. Instead, the object is a construct, and this construct has been made by a mind, and the mind has constructed it to explain or to make the claim that when this object is present, the evolution of the universe is going to change in this particular way in its environment, right?”