Hi,
Thanks for the query.
Yes, its possible to make use of same set of colors across different chart by implementing a custom theme file according to your requirements.
For further reference regarding FusionCharts custom theme file please visit the following link.
http://www.fusioncharts.com/dev/advanced-chart-configurations/theme-manager/creating-new-themes.html
For further reference regarding implementation of custom theme please visit here.
Hope this will help you.