A problem with the existing settings in Excel is that you cannot change more than 6 default chart colours. You can set up your own customised colours to use for each series but only up to series 6 (you can see how to do this at the bottom of the page).
A workaround to this could be:
Use the Chart Format Painter
Set up the chart the way you like it (colours manually set up) then use this going forward to easily take the chart format, including your colour scheme, and ‘paint’ it onto the other chart/s.
You can see more on the ‘Copy the Format of one chart to another‘ lesson.
This works as long as you have this ‘sample’ chart always visible to you.
Create a Chart Template
The other option is to create a chart template i.e. in the same place where you choose whether you want a line chart, or a column chart, you can have a template which is based on how you set up a chart including the colour scheme.
To see how to customise the chart template watch the example video from the Excel Charts and Graphs Course below