Yes, but it's not me being naive 8-), from the IET:
"The new (harmonised) colour cables may be used on site from 31 March
2004 New installations or alterations to existing installations may use either new or old colours, but not both, from 31 March 2004 until 31 March 2006. Only the new colours may be used after 31 March 2006.""a new version of Approved document P has been issued by the Department for Communities and Local Government (formerly the Office of the Deputy Prime Minister (ODPM)). This came into effect on Thursday 6th April
2006"So the idea that using red/black gets you around part P is quite silly because of the two year transition period for the harmonised wiring colours which came BEFORE part P was compulsory, so there's plenty of new coloured wiring that was done before part P.
Now if the claim was of an 'illicit' trade in any coloured cable dated before 6/4/2006 then that would make a little sense. Greg