I never recall seeing the zebra stripes in TMP, and the reference photos I used back in 1986 to build a 3D model didn't have them either. I don't see them in TMP or in screenshots from that film, and various models people have made of the workbee since then don't feature them, either. Heck, even the Drex Files had diagrams of them minus the stripes. You don't see them anywhere else in TMP, and knowing how Andy Probert designs stuff with functionality in mind, such markings are unlikely to have been applied where they are on the model for TMP, because they make no sense there: caution, waistline? I might be wrong, but I can't find any TMP era images in which the stripes can be seen.