
I don't think Natsume ever did.

Thats Natori san.

No, there's no such chapter. Natsume didn't saw it, only Matoba and Natori.
There's a fic about how he will see it, by the way. Here: https://www.fanfiction.net/s/10994925/1/The-color-changing-kimono

Strange. I also remember something like that, that someone was asking Natsume what color is the kimono. He answered it (gold, I guess?) And then he wondered what color will Reiko-san see if she saw it. Am I imagining things?

So I'm not the only one who read something like that?

I think it was in the anime… I also remember that! And since I have never read fanfic or the manga it must have been the anime. I also remember a scene where Natsume runs along a corridor and looks out to the kimono fluttering in the wind. I would like to see that again but I am not in the mood to rewatch the whole anime right now. Oh and I am pretty sure it has to be in the first 4 seasons… and it is NOT the season with tsubames blue kimono! (season1 ep6) Anyone with me on that?
The chapter where Natsume told the colour of the kimono which indicates one's spiritual power, like this one?: http://www.mangago.zone/read-manga/natsume_yuujinchou/mh/v17/c070.1/13/