Silvia,
You can save a custom template with a single color selected(via the Save As > SmartDraw Template command), but it is not possible to save a custom palette of colors unless the user defines them locally (individually). They are then saved in the localized settings for that installation of SmartDraw. If you are referring to the Themes feature, it is not currently possible to define a custom theme.
If you have further questions, please let us know.
Regards,
SmartDraw Support