You can easily customize the settings you have asked about by applying custom styles to these.
In order to do so:
1. From the project I sent you, copy CustomDialogsCss.css (it will contain the custom settings for the TrackChanges dialog) and EditorContentArea.css (it will contain the custom settings for the highlight text during the AJAX spellchecking) in your project
2. Add the DialogsCssFile="CustomDialogsCss.css" and ContentAreaCssFile="EditorContentArea.css" properties to the server declaration of RadEditor in order to register and apply these two files. Make sure you specify the correct filepaths;
3. Edit the desired settings in both files. For your convenience I've put comments in the CSS. Make sure you force the new values with the !important flag, otherwise they will fail to load, i.e:
selector
{
property: value !important;
}
Have a great weekend,
Martin Ivanov
the Telerik team