Maybe there is a character missing. Normally the Windows clients skips those files.
At least according to Path and Windows reserved characters and https://github.com/haiwen/seafile-client/issues/731 and https://github.com/haiwen/seafile/issues/1379
Here is also some important information missing: Which Seafile Client version? Is it only the : or are there other characters the issue arises? (keep in mind the correct behavior is to not sync those files to windows at all)