You need to create 3 separate rules in order to graphically distinguish each floor.
As I see now you have one rule, which works like this:
If the element is "Zone" AND the home story is (0. OR 1. OR 2.) <- note that I used a parenthesis here, which means any statement is true, it will apply the graphical override defined below.
To achieve what you want, you need to create 3 separate rules and add all of them to graphic override combination. (Combinations can have several rules that are applied in the order of bottom to top, if I remember correctly).
So rule 1:
Element type = Zone AND Home story = 0., surface = RED
Rule 2:
Element type = Zone AND Home story = 1., surface = GREEN
Rule 3:
Element type = Zone AND Home story = 2., surface = BLUE
And you combine these into a new combination, called something like "Zones by home story", and you have your rules:
Rule 3
Rule 2
Rule 1
Everything transparent
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