Adding Data Markers to graph

Ok, this is not as easy as it sounds.

I have about 10000 data points that I would like to graph. However, with this many points, line style does not show up, and adding Data Markers makes the line very think.

Is there a way to only add 5 or 6 data markers, similar to this (see pic).

Use additional data series where you only plot every 1000th point.

With that much data in a chart line colour is the only reasonable way of identifying individual series.