iDye Poly is virtually the only dye that will color polyester. In fact, it will color almost anything synthetic, including plastics and nylons, buttons, frisbee discs, Worbla & Thibra, 3D printed objects, toys, dolls, wigs, cleats, urethane coatings and more.
The dye comes in a dissolvable packet, so there are never any messy powders to handle: simply drop the packet in a pot of water, add the fabric or objects and bring to a simmer. (Need a lot? There's also containers of messy powder!)
An essential tool for cosplay artists!