Unlike in Britain, I don't think there is a specfic colour for telephone boxes in France. I think that most of them are built of glass and so are transparent anyway.
Telephone boxes in the UK aren't a standard colour anyway. The old GPO ones were red, but Hull COunty Borough Telephones had cream ones, which are still the standard for Kingston Communications. There are other colours - BT's newer ones are mostly transparent but red and greyish, and I've seen sort of bluish ones belonging to Mercury.
http://fr.wikipedia.org/wiki/Image:Paris_06_telefon_4567.jpg
