Frankly, the wiring on the new-style British plugs has become a real mess.

It started when the BT standard was copied into a British Standard, but the latter managed to get the terminal numbers written the opposite way around, so that 1=6, 2=5 etc.
I've also seen some cheap extension cords and adapters where the cord has been fitted "wrong way up," so that red & white are swapped and green & blue are swapped. It doesn't matter if the two ends are both done reversed of course, but if you cut a cord to re-terminate one end it can cause real confusion at first.

I've also seen some recent cheap imported cords (China, usually) which have started using American spec. flat cord, so the line will be on black & yellow (which wire is ring and which tip is anybody's guess!) and the bell wire may be red or green. As I said, it's become a real mess. [Linked Image]

By the way, the old phone cords which were hard-wired to a wall junction box were also red, blue, green, and white, but the green & blue were wired differently. On a basic phone green was a bell return and would generally be strapped to the white at the box (or to a local earth on party lines). A separate earth would also be used on PBX extensions for recall.