Cook the farro according to package directions until al dente; then set aside to cool.
Place the farro in a large bowl and add in the grapefruit segments, orange segments, feta crumbles and mint.
Make the dressing. Place the dijon mustard in the bottom of a medium bowl, then whisk in the orange juice. Keep whisking, slowly drizzling in the olive oil until creamy. Add in the salt/pepper then add to the farro bowl, tossing to combine. Season to taste, adding in more salt/pepper as needed. Serve at room temperature.