If you have a ms-word document (or oo-writer document) with special text-colors, which do not exist in your openoffice-configuration, then this special color is listed in the format-character - dialogue as "userdefined" (or similar, in german it is called "Benutzer"). But it is not listed in the very similar dialogue which you get when clicking on "Format" in the search-replace-dialogue.

So there does not seem to be a chance to change this color to a color known by openoffice, using the search-replace dialogue, i.e. the only possibility is a manual change.

Adding all colors occurring in the document to the search-replace-formats - dialogue would solve the problem.

Regards, 
Tom