Before extrusion, the HDPE can be pigmented to yield color-coded pipe. Common PEX tubing colors are natural (hazy clear, unpigmented), white, black, red and blue. The red and blue colors are used to help plumbers and homeowners distinguish between hot and cold water supply lines.
No, there has never been a US President from an independent party; however, at the time of his presidency, George Washington was not affiliated with a political party at all, as there were no parties in the brand new United States of America.
Hence an ex-president could (in theory) run for a seat in the House of Representatives, the Senate, or for any state office such as Governor. John Quincy Adams is the only former president to have served in the House of Representatives after his presidency. Andrew Johnson is the only former president to have served in the Senate after his presidency. Interestingly, it might be possible for a former President to run for the office of Vice President. This would seem strange, given that the Vice-President is expected to replace the President when necessary, and would thus seem to be in violation of the no more than two terms rule.