A sign nailed to the lifeguard station explains the meaning of the flags. The yellow stands for "moderate surf conditions"; "exercise caution." Moderate is somewhere between calm and rough. The purple flag means: "dangerous marine life." Here the danger is mostly in the sting of the Portuguese man of war. The flags do not need much interpretation, except perhaps to reflect on "moderate," as you wade into the surf and feel the waves slap and the tide pull.
There are other objects that I elevate to "signs," a mess of keys in the sink, for instance.
Asparagus fern--fresh green against pink.
And this green doorway with its single plant.