#roger fender

There's a pretty big industry surrounding feather products for Stratos, which includes preening oils for all sorts of purposes (waterproof, long-staying, scent) and, of course, dyes! Since they are formulated for Stratos feathers, they have to be acidic but they don't cause major damage. There's two types of dyes often used: powdered and liquid. The powder version is more for temporal use, often as decoration for festivals and events, or for camouflage in the military. Some are waterproof, some aren't, most have solvents to quickly wash off.

Liquid dyes are meant to be more permanent, binding to the feather and lasting 'til it gets moulted out. They can be painted on, or placed with an air brush, and lots of wing stylists offer already-made stencils or completely custom designs. As dyes often do, a bit might run off with frequent water exposure. Definitely don't go for a rain flight after a fresh dye...

Now, bleaching feathers in general is more damaging and it's recommended to never bleach flight feathers if you need to fly. The process actually causes damage, making the feather less flexible, less waterproof, and more prone to breakage. Per moult, Stratos are recommended to never bleach more than once, if at all. Similarly to hair, a black feather when bleached may turn an orange-golden colour, not white.