Midnight blue dinner jacket with black trousers?

Methinks not. Even if the rules permit it, I think it would be similar to wearing different pieces of the same colour---- just looks off. What do i know though?

You can wear colored peices when the jacket is obvioulsy different from the pants (Ivory or bottle green jacket, black or midnight blue dress pants) but when it's too close of a color the only way it's still elegant is when they are the same color but two obviously different fabrics such as black velvet jacket, black wool dress pants.

However, if the jacket were midnight blue silk velvet, black barathea pants would be OK.

But i wouldnt get a Dinner jacket in midnight blue with matching or close fabric pants in black.

No ....Mismatch are casually acceptable but no in a formal or code orientated event...

Nothing worse than a very formal outfit spoiled by a mismatch....

+1 to all responses. Black trou would be fine with a white (Casablanca) jacket or with a true smoking jacket - whether blackwatch plaid or solid velvet as notably worn by Christopher Plummer at the Oscars: