Caroline,
#78 - logo converted to grayscale. This was a straightforward conversion without any adjustment. If you like, I can submit another version that uses some deeper grays and/or black to create more contrast (I can provide all of these versions if selected as the winner)
#79 - All black version (fax cover sheets, invoices, etc.)
#80 - White on black.
#81 and #82 - Two versions of the standalone mark. If you like, I can try to incorporate an "S" and "F" into one of these (I think it depends on your planned use for the mark style).
Jason