There are a number of ways that it can be done. It all depends on the customers desired level of perfection, quantity of order and budget.
5 clrs: Base, Yellow, red, Blue Top white.
6 Clr: Base, Yellow, red, Blue Purple Top white.
9 Clrs: Base white, Yellow, Green, red, Magenta, Light blue, dark Blue, Purple, Top white.
If you discharged that base, then you could do a full 10 clrs.
In my experience, Purple is much harder to create "well". Always depends on the PMS clr used of the Red and Blue so I usually prefer to use one.
If someone had a bigger press and the customer was really picky and didn't want to see any dots, then you would print all of those tertiary colors as a spot for a more dead on approach.
It all depends on the desire. 9 seems to be the consensus.