Dave I can see your logic with that .
But being as well when the powers that be decided to alter the colours they neglected to issue a reg dictating how we should interpret ( I have yet to find one ) and subsequently use them , I went this way .
My way of thinking was Live is primary , Neutral is secondary and Earth is last .
With numbered multi-core , sequentially the Lives are first then Neutral followed by Earth being last , and any spare after that then being tagged down to Earth as well .
For 2 way I expect to see brown at the top in common , then black in way 1 with grey in way 2 .
On a side note , when it comes to any connections , unless already marked I go with live first then earth in the middle , with neutral last . This way if either connection should pull out / melt they have more chance of earthing out first .
This has been raised with me before , but as I say I am yet to hear a good reason why not to continue with what is now the pattern in our installs and has been since the change .