I forgot to say that the irony is that it was not very long ago that I was saying (I think here) that I would very much welcome 4-core flex with colours such as this one I've found....
...particularly in the case of small CSAs, it's probably fairly unusual to use 4-core flex for 3 Phase+E, yet it nearly always seems to be Brown/Black/Grey and G/Y. Far more commonly, one wants to use such a cable in single-phase applications which require N, E and two Ls (one often, but not necessarily, one 'permanent L' and one 'switched L') - in which case it would be far more logical/convenient to have blue, brown & G/Y (as with 3-core) plus an additional black or grey for the second L.
... and now I've found some of what I was 'wishing for', in my cellar!
Kind Regards, John