There are two possibilities that may suit your needs- graph templates and graph themes. They both allow you to save graph customizations for future use but are somewhat different in their approach.
You can use a Graph Template to have specific customizations set when you first create the graph. With Graph Themes, you can apply customizations to graphs after the graph has been created. E.g. You could apply a theme to go back and change old graphs.
Using either would also allow you to have other customizations saved besides just the plot color (if you wished).