Thanks

I think the xrefs are worth it because while a player of mahjong might know the term dragon tiles, he might not know what they are called in japanese

https://mahjongcollege.com/term/4454/
  三元牌（読み方：サンゲンパイ）とは、白・發・中の3つの牌のことを指す麻雀用語です。
  
https://majandofu.com/mahjong-glossary-sangenpai
  三元牌とは麻雀で使用する牌の種類で、白・發・中の牌の事です。
  
https://media.jannavi.net/mahjong-sangenpai/
  三元牌とは、字牌の「白・發・中」の総称です。
  
https://ja.wikipedia.org/wiki/麻雀牌
  三元牌は白發中の3種である。

https://riichi.wiki/Jihai#Sangenpai
  'The sangenpai 「三元牌」 (lit. three foundation tiles) are three tiles, originally representing the three Confucian values. These tiles are quite distinctive, often brightly coloured. In English, they are most often referred to as the dragons, but occasionally they are referred to as the colours.'

"dragon tiles" by itself doesn't indicate that there are only three types of tiles. I think it's helpful to address the "三" in "三元牌" at least implicitly by adding cross references.

Naming these tiles "dragons" is an entirely English-speaking / western phenomenon, so I'm not satisfied with the single gloss by itself. I think adding cross references is the easiest way to supplement it. In Japanese there actually does exist unrelated terminology derived from the word "dragon" (ドラ牌) which adds to the confusion.

Every Japanese definition for 「三元牌」 begins by listing the tiles.

@@ -15,3 +15,3 @@
-<xref type="see" seq="2751420">白・4</xref>
-<xref type="see" seq="2833340">発・1</xref>
-<xref type="see" seq="2754230">中・1</xref>
+<xref type="see" seq="2751420">白・はく・4</xref>
+<xref type="see" seq="2833340">發・ハツ・1</xref>
+<xref type="see" seq="2754230">中・チュン・1</xref>

Are the xrefs needed? Anyone who plays the game knows what they are.

I think it's appropriate to display the readings here since they're not obvious or unique for the kanji