they didn't change his eye color. they were always brown all they did was make his iris' (the color part of your eyes) bigger. since they were smaller before you was never able to notice it. now that they are bigger you notice the color of them.Ash's eye color and hat were something else I want to talk/rant about; why the eye color change? I get the new hat but his eyes were great before this change. Totally out of left field I think.
i liked the episode it was different since no one ever mentioned isshu to ash before hand until they got there.