GF Umber & Cream Pullman carriages - different roof colours?

[dannyboy]

Whilst on my jollies last week, I bought two GF Umber and Cream Pullman coaches with grey roofs. I have seen the same description carriages available with white roofs. Can anybody tell me why the difference please?

[exmouthcraig]

Our rake of 11 are all early releases Danny and all have white roofs, the grey ones seem to be a batch of later ones, presumably as the white roofs lasted all of the minute they left Metro Cammel they were covered in all sorts of muck and they never went white again 

Unless Met Cam NEVER painted these particular Pullmans with white roofs and GF are being exact and their leaving their factory with the same paint scheme