This has nothing to do with the thread subject, "NTFS is grayed out". To make it active install the ntfs-3g-ntfsprogs Alt-F package.
That only allows you to format drives using ntfs and has *nothing* to do with "Windows 10 see's folders but does not let me write to them".
Try using ftp (using filezila?) to write something into the folders.
Be sure you have setup users (Setup->Users) and are using the same name/password in Win-10. Always describe the exact steps you take and post the error messages