Socket replacement wiring
It looks like you need to connect:


Red to the 'L' terminal (brown)
Black to the 'N' terminal (blue)
Green to the earth terminal (green / yellow)


Your wiring is the in old colour scheme and the socket is marked with the new (harmonised) colour scheme.

(By the way, from the photo, the existing wiring looks like it could be the (very) old rubber insulated type of cable, which you may well need to seriously think about replacing).