On 28 May, 07:30, David Hansen
wrote:

It was "dreamed up" by the IET. They gave members and interested
people some time to cogitate on the matter. To make cogitation
easier they provided a table of wiring colours in (IIRC) at least
western Europe. I couldn't think of a better solution to the one
they implemented,

Start wiring purple.

The whole problem stems from the problematic re-use of blue & black.
So we shouldn't have done this - there's hardly a shortage of other
colours.