In a round-about way, that's what conditional formatting is. (in fact,
if you click in the cell, you don't even need to see an actual formula
at all!) In the conditional formatting dialoge box, that's what the
conditions are. They are testing the cells you tell it to, and
testing what the values are. And based on that cell's value, it will
FORMAT the cell however you tell it. If this, then do that...etc.
In a cell, there's no way to type "=if(.....)" and incorporate colors
into the formula. What I mean is, making cells different colors is
formatting it, not a formula per say. "=if(B2=4,red,green)" does not
make sense. You could use VBA, but that would make it a more
complicated than it needs to be.
I tried your original request and it works out just fine.

dk