1.
would is the modal used for the consequent clause of a conditional structure.
If that suit were navy blue, I would buy it.
If that suit were black with gray pin stripes, I would like it better.
If it were gray, I would like that suit better.
The condition (
if-clause) is implicit - not explicit - in the given sentence.
in navy blue instead of
if it were navy blue (in color).
2.
suit is a noun. a suit of clothing; matching
jacket and pants (and a vest for a three-piece suit) - what color?
- blue - what shade of blue? - navy blue.
There is no article because there is a demonstrative adjective
that. You can't have a demonstrative and an article.
this suit, that suit, a suit, the suit, but never
the that suit, that the suit, a this suit, this a suit, etc. I think you are misinterpreting demonstrative
that as complementizing
that.
I like this suit, but I like that suit better.
This suit is available in blue, but that suit is not available in blue.
I like that suit, but it's black. Do you have that suit in navy blue? -- No, but we have it in gray.
3.
Why isn't there an article? is perfect grammatically, idiomatic, and appropriate for the situation.
![Smile [:)]](/emoticons/emotion-1.gif)
CJ