I posted to the end of "The Cube" thread, but I thought this might be more central. I have located a source, C&S plastics, for colored PVC pipe that is free from pthlalates and heavy metals, with the color throughout the pipe, not "painted" on. The company sells it for use in bird toys as well as dog agility equipment in addition to other uses. It comes in smaller diameters, down to 1/4" (white only this small), and I plan to order some to make enhanced play space for my cagetop playstands (and maybe a portable gym for Scooter). They also see the connectors and they have a variety of bright colors. Since I have not found any other similar source on the web, I'm guessing this is where most of the colorful PVC stuff we see in catalogs comes from.
The site appears to be geared for resellers, but I emailed them and got a very prompt response -- they are happy to fill any size order (pipe in units of 10').
Here is the link again: http://www.candsplastics.com/