oh I get what you mean. So in the book they refer to the fact the armour colour is created with splattered pigments instead of any sort of general colouring.
Perhaps test it on a model? Any model in armour would work I imagine; for a base idea. But in terms of telling you how'd it look without actually doing it, well that'd be rather hard

I say just give it a go! If you havent got the exact colours you can simply use another colour range as a tester, say reds, or blues or yellows or any colours you have
Question is: How would you achieve your splatter? You could use a brush and flick lightly, alternating colours frequently to get a good mix in the layers. You could use an airbrush on a very low PSI to lightly dust the models, alternating colours once again. Err not sure how else you could splatter it. You could sponge it on too, to get a very rough effect, or stipple it with a brush to get a similar look.