Here's how to format chart markers (points) for different data series in Excel:

1. Select the Data Series:

* Click on a single data marker to format only that series' markers.
* Click on the legend entry for a data series to format all markers in that series.
* Alternatively, hold Ctrl and click on multiple data markers or legend entries to format them together.

2. Access Formatting Options:

* Once you've selected the data series, the Chart Tools context menu will appear.
* Click on the Format Selection button within the Current Selection group.

3. Customize Marker Options:

* In the Format Data Points pane on the right, navigate to the Marker Fill and Marker Border sections.
* Marker Fill: Choose a fill color, gradient, pattern, or texture for your data markers. You can also adjust transparency.
* Marker Border: Select a border line style, color, and thickness for your data markers.

4. Additional Options (Optional):

* Marker Size: In the Marker Options section, adjust the slider or enter a value to change the size of your data markers.
* Marker Type: Choose a different built-in marker shape (circle, square, diamond, etc.) from the options available.

5. Apply Formatting:

* Once you've customized the marker fill, border, size, or type to your liking, click Close on the Format Data Points pane.

By following these steps, you can format the chart markers for each data series in your Excel chart with different colors, styles, and sizes, making your chart visually clearer and easier to interpret.