Having trouble a bit ....  So there is a color table associated to BOTH text color and highlight color in the RadRichTextBox.  So these are represented by tags.  I understand so far.   So if a series of text characters have a default of Black. and I choose to change only some of the text characters to red .... is this an example of changing from a default to a color definition omitted in the color table?   And Is there a way to setup the RadRichTextBox in a way that it could be possible to change any part of the text character color or any part of the highlight and export it?   It appears that IF we new the color table that we MIGHT have confidence that we could be compatible when we export?  Is that a true statement?

Thank you Todor for this. 
 I wanted to emphasize  the Other Most Significant 
"Readers" to be Listed in your explanation above . . . .
No1:   Do not export to "WPF documents"  (both Flow or Fixed WPF Documents)   WPF Documents are provided as the default as a part of Visual Studio BUT render corrupted if exported from RadRichTextBox.    WPF documents Link at MSDN:   https://msdn.microsoft.com/library/ms748388(v=vs.100).aspx

No2:   Do not export to "WordPad"

Thanks a million for support Todor.   I wish that the RadDocument "Sections" and "Paragraphs" and "Spans" had a SELECTED EVENT HANDLER like Microsofts WPF Documents.  If we had this .... we would say goodbye to WPF Documents and Embrace the RadDocument provided by Telerik.