Hello
So ideally we want the roots to stay a healthy looking white throughout the entire grow...but this isn't always 100% doable. Are you having any leaf symptoms appearing since this root change happened? If not that's very good and you may have caught it before any negative effects could set in.
Doing the h2o2 for now is a good idea but it's usually a short fix...if you don't already use a root product like hygrozyme, root shield etc. Those beneficial bacteria shields you may want to start one up. Because the h2o2 will kill the bad bacteria but it's also going to want to attack your good too.
Try the h2o2 and then reevaluate again in a couple days.