Another consequence of a subterranean existence...

Odours are rather more significant to the Noygooros
(lit. "Underworld.people") orcs as a means of recognition and even getting
around in the dark.
I'm thinking about trying to group odours into a spectrum or array of some
form similar to what people do with colours.  I mean, there are a large
number of different shades that can all be lumped together as "blue"-
cobalt, royal, sky blue, turquoise, denim, and so on.

Can you do this with odours?  What odours would you use as the "cardinal
odours"- the categories like blue, red, green and so on that can be broken
into different shades?

Help!  I feel like I've let my imagination take a leap that my logic can't
keep up with!