AFIK all the M56 vehicles had the ZF transmissions. (see attached PDF). I have seen some of the ZF blue stickers that have oxidized and turned sort of a bright metallic green color over time. (as opposed to the more flat-puke green colored GM sticker). Best to check the recommended fluid part number listed on the label to verify which you have.
edit: PDF was too large so just took a snapshot of the first page
Last edited by Melquin; 12-27-2009 at 11:25 AM.