Coloring the pieces of each side differently can limit the use of color in distinguishing between types of pieces.

Not really, because there are more than two colors. It is very possible to pick two different dark colors (black and blue), and two different light colors (white and yellow) where for each pair the "Spot the Intruder" game is just as easy, and then use blue and yellow for promoted pieces.

Most Shogi sets I have seen do not have red kanji for the promoted pieces, btw. They just write different kanji on them. (Well, people tell me they are really the same kanji, but in different fonts. But they look different enough.)

It's not for you to say what Japanese people would think, and it is not for Japanese people to judge whether one of my experiences feels more authentic than the other.

I am just relaying what Japanes people said, on the Shogi forums I visited, and at the OTB Shogi tournament in Kanazawa and Yokomama that my Shogi engine participated in. And you surely give a whole new twist to the concept 'authentic'.

I have not had any communication with them on this, but it would be as objectively false as saying that you are not playing Chess if you don't use Staunton pieces.

This has puzzled me too. We have no trouble recognizing a game with, say, Star Wars puppets as Chess. For Shogi that would be unthinkable. The Japanese seem to consider the physical representation just as much part of the game as the rules for how to move the pieces. That explains why the Japanese Shogi Association is so conservative in endorsing any kind of on-line play. They insist that the experience behind the computer screen must be as identical as can be technically expected to playing over the board with the prescribed equipment. Including the possibility to play illegal moves.

I suppose it must be that way, because the over-the-board equipment, being subject to physical limitations, is inferior to what you could do on a computer screen. (Funny story: when I was playing in Kanazawa, my program was of course showing the position as pictograms, even though the official board on which I had to perform the move used of course kanji tiles. And it puzzled many people, both opponents and audience, that I used different color pictograms for both sides. The said ro me: "How can this work? When you capture a piece, it has the wrong color." It did not occur to them that a computer can change colors at will.) So if they would allow people to use arbitrary representations, these would quickly move away from the traditional representation, and use one that doesn't hurt their rating so much. If they would have been confident that kanji tiles were the superior representation, they would not have little reason to forbid anything else. But as it is, they consider it cheating.

This is one of the most important reasons that a good game like Shogi has failed to conquer the world: people that try to popularize it usually have as their main agenda to spread Japanese culture. No to spread a good game.