The full sentence is “Their small, fine scales are usually brass or bronze in color, sometimes ranging to scarlet, rust, gold, or copper-green.” So a red one is kinda like a real life human with ginger hair; uncommon, but not weird. There’s also the bit about dragonborn with a particularly strong influence of their draconic ancestor shortly afterwards that says, “These dragonborn often boast scales that more closely match those of their dragon ancestor - bright red, green, blue, or white, lustrous black, or gleaming metallic gold, silver, brass, copper, or bronze.”
Rare, yeah, but still a valid possibility. But the main part I wanted to bring up is that the sentence you were referring to actually already includes “scarlet” as an ordinary colour, so the red one in the accompanying picture fits just fine
Official Dragonborn PHB description say Dragonborns are brown/rust coloured, with some being rust-copper green.
Artwork on the same page is a red scaled dragonborn.
The full sentence is “Their small, fine scales are usually brass or bronze in color, sometimes ranging to scarlet, rust, gold, or copper-green.” So a red one is kinda like a real life human with ginger hair; uncommon, but not weird. There’s also the bit about dragonborn with a particularly strong influence of their draconic ancestor shortly afterwards that says, “These dragonborn often boast scales that more closely match those of their dragon ancestor - bright red, green, blue, or white, lustrous black, or gleaming metallic gold, silver, brass, copper, or bronze.”
You omitted that the draconic colored scales are from extremely rare and isolated clans.
Rare, yeah, but still a valid possibility. But the main part I wanted to bring up is that the sentence you were referring to actually already includes “scarlet” as an ordinary colour, so the red one in the accompanying picture fits just fine
The player characters are generally adventurers fated to achieve greatness, for them the extraordinary is just ordinary.