In Reginald on Tariffs, Saki writes:
[Reginald]: I should like, for instance, a really prohibitive duty put upon the partner who declares on a weak red suit and hopes for the best.
What does it mean to declare "on a weak red suit"? Would "suit" refer to a piece of clothing or a playing card suit in this instance, and what is the significance of it being red? (There is also a reference to a "weak red tendency" at the conclusion of the story.)