Thanks very much. That’s a really useful resource though as you suggest, it doesn’t really cover the auxiliary troops. However, I’ve had some luck as I’ve found this, which shows what i believe is a medical orderly:

This would seem to confirm that in 1870 the dark blue was being worn by medical units, which is what I shall go with.
EDIT
While the Bavarian medic Max Lehner doesn’t appear to be wearing a Red Cross armband, there are plenty of images of Prussians wearing them in 1870.
Prussia adopted the first Geneva Convention in 1864, with Bavaria doing so in 1866. As such it seems reasonable to assume that by 1870 the Bavarians were also wearing the armband in the field.
/EDIT
If the supply wagon is an ammo caisson , then it seems likely that the crew would be in artillery dark blue, which would seem to cover it.
Many thanks.