BalkanExpress and christo, the livery shown in the first photograph shows Fiat built MU sleeping-cars in their SNCB / NMBS livery following the end of the TEN pool in 1995.
The model of the T2 sleeping-car, second picture down, shows the full TEN livery.
After the end of the TEN pool, many sleeping-cars just had the TEN logo painted out, as on the picture by Morten S. Sørensen, taken in København H / Copenhagen on 4 May 1996 (sleeping-car number unknown, but clearly one of the carriages built in Germany by WMD). Later this transition livery was replaced by the full SNCB / NMBS livery.
Two possibilities : OSE repainted the sleeping-cars which wore the full SNCB / NMBS livery, so that they would match other ex TEN sleeping-cars which OSE also bought, or the OSE sleeping-cars in almost TEN livery did not receive any other livery before they were delivered to Greece, so OSE just kept the livery as delivered to Greece and just added their markings.
One way to prove this either way is by checking each carriage. Most of them are illustrated, with the corresponding number, on
http://wagonslits.de/, see Forum, then Album at the top of the page.
Are or were there any OSE MU sleeping-cars in the full SNCB / NMBS livery, but with OSE markings ?