You can achieve this by modifying the external RadEditor's dialogs to use RadColorPicker instead of the RadEditor's built-in ColorPicker control.
In the following demo you can see how to customize the editor's built-in dialogs: Customize Built-in Dialogs
For you convenience I have attached the modified CellProperties.ascx
dialogs that use the RadColorPicker control.
Note that the RadEditor's built-in ColorPicker
has different methods to set and get current color. Please examine the code and check the comments about the changes that were made.
In addition, AddCustomColor
feature is planned to be introduced in the next major release (Q1 2010).
the Telerik team