What I would try first is, duplicate the video track, stack it, isolate the affected area with a soft-edged mask/crop tool on the top layer, then try using the 3-way color corrector on it. It may take multiple iterations of this technique, one for each colored area, but you can use the eyedropper tool to sample the “good” color from right next to it. Apple Color has even more powerful tools than the 3-way CC does. You might want to pose the question in the COW’s Apple Color forum.
If the camera is in motion, your project is more complicated, and you’ll first need to stabilize the footage with a motion tracker, or resign yourself to keyframing the crops and masks on the FCP timeline.
Another way to go, if this is just a few seconds, is to export the clip as a series of stills into photoshop, and use things like the healing brush, levels adjust and other tools to fix each frame, then re-import the repaired frames back into the timeline.
Let us know what you did to finally fix this.