We've always used the Orange conduit here for underground Power services, at least as far back as the 50's.
Mind you, the older (first) form of PVC conduit here was nothing short of rubbish and we are still digging it up today, to find that most of it has collapsed.
Green conduit is used here for Telecom's cabling and Yellow for Gas.
Just as a little note, I once connected up a shed for a guy that pulled the submain cable through 2" Galvanised Steel water pipe.
The cable was 2.5mm2 and he was remarking as to how hard it was to pull it through.
After hearing that I went to get my Megger, it shouldn't be that hard to pull and I suspected cable damage.
The Megger confirmed this and up came the pipe-work!.
4 90 degree elbows.
I dismantled the work and pulled the cable out, to find all 3 cores bare at one part of the cable, the result of a huge burr on one of the pipe threads.
That was lucky!.