Hello,
One relatively easy way to do this is to use X and Y as you have, use DayOfWeek as a graph marker by right-clicking on this column in the left pane of the data table and selecting "use as marker", using Year in the Overlay role, and using both the "Line" and "Points" elements in the graph.
This has the ancillary benefit of not requiring the analyst to remember which of the symbols correspond to "weekday" and which correspond to "weekend".
Cheers,
Brady