Event marking time series plot

I have two time series (f(x), g(x)) plotted in one figure.

I need to be able to mark different kinds of events on each of the time series and then retrieve the data from the figure. For instance, a green circle would be the marker for one kind of variable/event on f(x), a red star for a kind of event on g(x). Ideally, I'd like to have a GUI with a palette of icons I can click to switch variable markers. I only want to be able to mark points on f(x) or g(x). Once the plot is marked, I'd like to be able to get the x and y coordinates of all the red stars on g(x).