I agree, the rule says no all white, but think about the REASON for the rule. The NFHS wants officials to be able to quickly see if the mouthpiece is in. With this type of mouthguard, it's extremely obvious it's in.
The interpreter is using some common sense, applying the REASON of the rule if not the WORDING of the rule. We teach officials to do this all the time: call WITH the rulebook, not BY the rulebook.
I don't have a problem with his interpretation, and if it ever went to court, it's an easy win for the officials: was the color of the mouthpiece the proximate or contributory cause of the injury? Of course not. Was the player wearing the mouthpiece? Yes. Could the official easily see that he was wearing it? Yes.
Thank you, case dismissed.
I would sure rather see this type, even in all white:
than this, which is legal because it isn't "all clear":