I can't answer your specific question directly but I can tell you that there is furniture grade PVC in black and many other colors. I use it myself. On the exterior of my tanks I use regular white Sch 40 PVC plumbing pipe but on the inside of the tank I use black furniture grade PVC as it blends a little better.
You can find it on Amazon and the manufacturer is FORMUFIT.
Wondering what the difference is between furniture grade PVC and the commodity stuff you'd get at the hardware store? Furniture grade doesn't have a text line on the pipe indicating size or anything else. It also seems to be a slightly softer product to work with where some of the commodity PVC resins are close to brittle.