Plastic that’s got a lot of color (especially black) is very, very hard to recycle. Getting the color out so you can make like-new, colorless plastic makes the economics pretty much impossible.

Should recycled plastic that isn’t colorless be accepted? Yep. But basically every manufacturer that uses recycled plastic only accepts colorless stuff. Even if they’re going to turn around and dump a bunch of pigment and dye into it! (Or especially if they’re going to do that. They have specific color targets.)

So, for now, if you buy something that’s made from recycled plastic but isn’t clear and colorless, that plastic is now outside of the recycle-able ecosystem. It’s a bummer.

But there are ways to get around that coming online. One is to turn the plastic polymers back into monomers (the building block molecules). It’s sometimes easier to separate out the pigments and dyes once you have a chemical soup of monomers instead of a block of plastic. Then you take the purified monomers and repolymerize them. Bam, you have recycled plastic that’s nearly indistinguishable from new.

I worked on a chemical recycling / depolymerization project for a couple of years. That tech is currently being scaled up into a big plant that’ll actually churn out like-new plastic from really crappy input material. Pretty exciting stuff. (As long as the business and engineering guys running the project now don’t ruin it.)