Suppose I have one green hat and one blue hat. How should I describe them? Each of the following sounds flawed to me.
A green and a blue hats.
This doesn't sound grammatical.
A green hat and a blue hat.
This sounds redundant, particularly if it's a long word instead of hat.
Green and blue hats.
This doesn't capture that there's exactly one of each color.
Two hats, green and blue.
This is ambiguous, because each hat could be green and blue.