1. You will surely look dull and boring.
2. It is one of those unwritten rules in fashion that never match a darker colour with another darker colour if they are not the same colour.
Meaning you can wear black over black or navy over navy but don't mix them.
In my experience as a fashion image consultant and an entrepreneur for distribution of imported high end men's fashion for over 35 years, I still have to come across black and navy combination made fashionable, in all the fashion shows I attend internationally.
I urge you to read fashion magazines like GQ and others, to follow the latest fashion trends. If you are serious about your dress sense, invest in attending fashion shows and get yourself a good image consultant to advise you on what or what not to wear, latest fashion trends, formal business dress, leisure and smart casual dress, personal grooming etc.
Some image consultant will even go the extra mile by offering you services like:
1. Hooking you up with a nutritionist.
2. Getting you a personal trainer.
These are necessary for keeping and maintenance of a good and healthy body that doesn't flactuate from time to time, thereby causing you a fortune in terms of replacing your wardrobe.
Good image consultants will even keep a record of all your jacket, pants and shirt measurements, your shoe sizes. This info comes in handy when it's time to replenish or add on more clothing to your wardrobe.
I have clients who only wear custom made clothing. Depending on their line of work, for a business executive, I normally recommend the acquisition of not lesser than five suits per year, three dress jackets, eight pair of trousers, sixteen formal shirts, four pairs of shoes ( 3 black and 1 brown), one navy blazer and two pairs of jeans ( jeans are an all rounder, they look good with a white shirt and tie over a navy blazer with black shoes).
Lastly, make a statement. Dress well for your own confidence. Dress for success.