Red plates are temporary transit ones (de, en, fr). It uses a standard registration number (here, DT-..., was given in early August this year), but this status is usually granted for a 6-month period (from three months to one year in fact, depending on the situation of the car owner - fr). It enables to purchase a new car with VAT and customs duties exemption and allows to travel throughout Europe.
The expiry date of the plate is shown by the 4 figures on the right side, which are in fact a month (on top) and a year (at the bottom). I assume that if the vehicle stays in France after the departure of its first owner, it regains standard white plates once sold and taxes paid...



For the record, there is no longer specific export registration/plates in France since the 2009+ SIV (Système d'Immatriculation des Véhicules). A temporary plate with WW is enough: it's valid for one month and can be renewed for another month.
The only difference with the WW plates usually used on new cars is the lack of local reference on the right part of the plate (and the VAT exemption when purchasing the car ):