If they had to fix chimerism, it would be implausible to do it after the organism is grown up. It would be implausible even if you froze time at the exact second of fetrilization and tried to fix it. It simply cannot be fixed using modern technology. But if it were fixed, the eye would slowly turn hazel. The pigment of the eye is similar to the pigment of the skin. So just how your skin gets lighter if you don't go in the sun for a few weeks, the eye would also change color over time (note that these processes would still be somewhat different because one is an environmental change and the other is a genetic change; I was just drawing an analogy).