Hey nice, clear pics! You may be able to use the tip of a sharp knife to slip the wires out of the connectors and swap them. Just be sure to get the wire colors in the same position..
Likely you only need the red and black to run the fan, yellow being the RPM sensor.
EDIT: Here's a couple of pics to help. Those tangs are delicate but can be swapped around, I've done a few myself with fans and front panel connectors.