Black is strong and powerful but can also evoke negative feelings related to death and fear, which should be considered before using only black and grey in a design.
All the great films made and photographs taken before color film was available. Television was black and white when the first televisions appeared in homes in the 1940's and color didn't become affordable until well into the 1960's. Retro.
Daring, provocative, trend-setting or expensive.
When I see black and grey I see the black cars, SUVs and limo's that are black with tinted windows and are carrying people of power - the President, the Governor, the Mayor - and often include men in black protecting them.
The temperature of the black and grey colors are cool to cold and hard like tools, steel, mechanical gears and factories.
Black represents death in our western culture and can also represent something, as well as someone, that is lifeless. A dead engine or a junkyard.