That's polybutylene piping.
visit
Polybutylene Plumbing - What is Polybutylene? for a short description of the alleged problems with PB piping and fittings.
I usually recommend replacement of PB piping and point the client to the web for information. I explain that a web search is going to result in many many links to companies who want to replace the piping for profit, and very few links to anyone defending PB.