You may have noticed that when you changed an option, the next time you drew something the options applied to all of the previous lines that were drawn. That's not a very good user experience. The user expects that when they change the pen options it will only apply to the next thing they draw, not everything.
In order to get that to work properly we will need to add more data to each action than just a list of points. We also need to know the color, width, and opacity to draw the points with. For that we need an object to hold all of these values.