I did for a moment wonder if it was a poisson d'Avril, given the date - but clearly not.
On the subject of tagging, would RENFE have allowed a tagged set across the border?
Avril is a multi-year joke, as you know (don't think the spanish do April fool's day though I could be wrong).
Talgo, rather than RENFE, are responsible for the certification work. The coaches have been standing around for months and years, I saw one at Fuencarral last year that looked awful - so thousands of RENFE customers a day were seeing it. A web search for 'Talgo Avril grafiti' throws up loads of pictures. Cleaning it all off must be part of the pre-delivery checks.
When, if ever, RENFE start leaving several sets overnight in Paris and Marseille I imagine the nice white body sides will get 'improved' frequently, much more suitable than SNCF's colours for making your mark on.