How can we change the direction of a DC motor?

Yes, you can change the direction of a DC – motor by changing the field wires or by changing the armature wires.

Only take care, that you change only the field or the rotary field. If you change both at the same time, you don’t change the direction.

By changing the polarity of either armature or field, field terminal are generally not change as open field winding on running dc motor is a dangerous situation so reversing the armature polarity is most viable method to reverse the direction of dc motor.