For those who don't know what I'm talking about, the Tertiary Color is often "that dark color" in an accessory used in small details, such as the handle of the Side Blade or the candles in the new Grand Topper.
However, there are others accessories where this Tertiary is often the "Primary" color, such as the Cat Tail, the Valkyrie Wings or the Hairband, to name a few.

Being so notable in some of the "most wanted" accessories, wouldn't make sense to add this info to the Wikia?