Sharpie Filament Color

It may not be a replacement for true colored filaments, but now you can add any sharpie color you want to your filaments. 

I've tested a few filaments and found that matte white and clear filaments do the best at taking the color.

Pictures above show a half blue half orange dragon, and then just half green and I left the other half empty, giving a cool gradient effect.

The bottom includes a hole to press onto a standard Bowden tube, for my use case (Direct drive) that's all you need to keep it in place. You may Remix it to work for your extrusion system.