For the absolute best long term no fuss tubing, I would recommend EPDM tubing, like EKWBs ZMT (zero maintenance tubing). But it is black only.

If you want coloured or clear, I have used hardware store tubing. But I was accepting the possibility that it might go wrong and I might have to do some serious cleaning or change coolants. Also, I only used it where it couldn’t be seen so that if it turned colour it wouldn’t matter.