I don't understand. I don't understand Korah's halachic question to Mosheh Rabbeinu. (as reported by Rashi)
פתיל תכלת הוא בחינת מה שאמרו חז"ל: במקום שאתה מוצא ענותנותו, שם אתה מצא גדולתו - וכן להפך
We know that there are many halachoth that even though their ways seem peculiar, any other way does not fulfill the obligation. Why did anyone think that Korah's question was legitimate?
What was Korah's question? Here it is: If you have a whole garment, and adding a little blue (tcheleth) string permits the entire thing, why wouldn't an entirely blue garment be permitted outright? (without the addition of a little blue string.)
To me it definitely seems like asking: We don't wear tefillin on Shabbath because tefillin is a sign (ot) of HaShem, and Shabbath is a sign. If I wear tefillin on Shabbath, do I need to keep Shabbath?
Of course you need to keep Shabbath!!
What was Korah's real argument, why did it hold water, and why was it still wrong?
Perhaps I could understand it like this:
Tcheleth, the blue color of the tzitzith, as Chazal explain, is there to remind us of the Kisei HaKavod (the Throne of Glory) a testament to HaShem's greatness.
Basically it could be that Korah thought that if a small testament to HaShem is good enough, then certainly an entire garment colored to declare HaShem's greatness should be even better.
We can even understand how this is at the source of his claim to the Priesthood: He saw that Shmuel HaNavi would come from his line, and Shmuel HaNavi, Chazal explain, was 'equal' to Mosheh Rabbeinu and Aharon HaKohen combined. So, Korah could have thought: Aharon HaKohen is great, no doubt, but my line is even greater and if it is an honor to HaShem that Aharon HaKohen should represent Him, it would be an even greater glorification of HaShem's name if I were the Kohen Gadol.
The key lesson that Korah, according to my limited understanding, didn't pick up on, and perhaps it's only clear in hindsight, is that HaShem doesn't want ego and glory and pride, he wants us to be humble. Chazal teach us that in the same place that you find HaShem's humility that's where you find His greatness.
We see this lesson in practice: Har Sinai was chosen as the place to reveal HaShem and the Torah because it was a small and humble mountain. Mosheh Rabbeinu was chosen to receive the Torah because he was the most humble of all men.
Humility and Greatness must always go hand in hand. This is perhaps why the tzitzith only has a little string colored to remind us of the Throne of Glory, of HaShem's might and greatness. Because on the tzitzith, where we find HaShem's humility, in a single strand among many, we find a hint at HaShem's greatness.