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Came up empty as far as finding a trope.
I feel like that's overly specific and doesn't have much narrative meaning absent any other information. Having not read any of Wings of Fire but knowing a thing or two about Dragon Tropes in general, dragons come in many colors and tend to have Pride as a common trait. It makes sense that a dragon would have pride in their own tribe and the common dragon colors for that tribe.
I think there could be room for some kind of Favorite Color Based Characterization trope where a character expresses "My favorite color is (color) because it's the color of (noun)." It's not just a stock quote; it succinctly reveals something they value above all else.
Could be worked into a subtrope of Transformation Name Announcement.
Silver and gold, silver and gold
A character's favorite color is their own natural body color. Example: In Wings of Fire, there's a dragon named Carnelian who has red scales and also says her favorite color is red.