The only tool that RadEditor offers for code highlighting is called "Format Code Block". There are two other tools that offer a coloring functionality - the Foreground Color and Background Color split buttons.
You can examine how they works in our online demos: http://demos.telerik.com/aspnet-ajax/editor/examples/default/defaultcs.aspx.
If this does not suit your need you can create a custom tool that achieves your desired functionality, as shown in the following online demo: http://demos.telerik.com/aspnet-ajax/editor/examples/customtools/defaultcs.aspx.
All the best,
the Telerik team