Yep, but they aren't used in tailoring. They are smithing items, but more commonly used for donations to the Britain Library collection.
Red & yellow come from Dragons, Greater Dragons, and Drakes (brown ones give the yellow scales)
White from White Wyrms and half of the Serpentine Dragons
Black from Shadow Wyrms and the other half of Serpentine Dragons
Green from Swamp Dragons
Blue come from sea serpents and Deep sea serpents (and are labeled "Sea Serpent scales")
any color can come from Ancient Wyrms
one of any color (typically matching their armor, if any) comes from the Chaos Dragoons (both types)
20 of each color come from Rikktor.
Blue dragon scales (from dragoons and Rikktor) turn to sea serpent scales when they refresh, and stack with the sea serpent scales.