IBM 5280 User's Setup Procedures page 17

8. Read the following four steps (a, b, c, and d) before
connecting the data station cable.
a. Look at the data station socket with the green label. This is
where you will connect the data station cable.
Yellow Label_II
Green Label
"'II
Back View of the 5281
b. Find a cable connector with a green label. Read the identification
label to be sure that it connects to 5281.
c. Position the cable so that the IBM logo is on top; then push the
cable end into the socket (make sure that the colors match).
User's Setup Procedures 11