Make sure the correct ribbon is installed. The color ribbon for the Fargo is YMCKO or YMCKOK. YMCKOK is the double-sided ribbon. The ribbon that only prints black is the K-resin ribbon

In printer properties, make sure that the printer preferences "sees" the correct ribbon.

If all the above is correct,

• go into printer properties.
• then preferences
• under the K panel Resin tab, make sure Print YMC under K is selected.