I have 3 stamps with red, black and blue cancels that glow orange under UV. Were these common and what purpose did they serve? I think they are permit cancels? Also are why do the stamps tagging and paper glow differently?
Yup, permit cancels. Many fairly modern inks (including stamp pad ink) have optical brighteners among other things including components that glow under UV, so this is probably what we're seeing. Different ink mixes (say, from different manufacturers) would glow differently. And these happen to glow orange.