Colors alone, the mind associates a crisp white shirt with blue jeans (or trousers) as a "classic" (or "uniformy") masculine look.
The idea is that the color below forms the base to "support" the color above.
Imagine the picture below without the jacket. While the fit in the picture is impeccable, white trousers and navy shirt look better on women, IMO. Why? I haven't thought that far yet.
Manton is referring to one's own personal "rules" in this thread, I think? No right or wrong here.