The single suit – that is, a suit for someone who rarely has cause to wear it, and thus has just the one suit.

This is often a “wedding and funeral” garment, as it will only be worn to an event where a suit is mandatory.

In such a case, the suit needs to be as broadly appropriate as possible, so that the wearer will not be out of place at whatever event causes him to don it.

A dark, conservative suit is what you want; black, navy blue or charcoal gray are all equally acceptable. However, if you have to choose one, lean towards charcoal gray as it is perhaps the most versatile.