For a casual home barista this is pretty realistic I'd imagine:
- use the grinder normally for a while
- grind 18g of green/light beans
- grind 18g of dark beans
- look at how much light coffee there is in the dark dose
My flatmate uses my (Sage) grinder as well as me and we use different beans. By eye the amount of his ground coffee that comes out when I grind mine is pretty small.
Perhaps you could do something clever with dye or flour or UV or sieving or magnets or something but I'd be wary of changing the clumping behaviour
I don't have appropriate beans in at the moment - someone give it a go and let's see what we can see?