"in the paint store they mix all that from a dozen or so base colors"
Apparently one of the colors favored by many of the Old Masters was what is today marketed by art suppliers in tubes as "cold black." Interestingly, it is almost the same color as "lampblack," which is one of the tints used by by paint stores in mixing up their colors. It is a black that, when a little white is mixed in, makes a gray with a distinctly blueish cast. When used alongside the earth tones that dominated in those days, it is amazingly blue, and even makes a green when added to yellow.
I frequently use black in abstract work but never in my representational stuff as it tends to flatten surfaces and straight black and white to make a grey tends also to be lifeless. I use color mixtures that together read as a very deep dark blackish hue but really is colorful and lively. The mix could be anything but many times I mix pthalo blue and green, maybe some alizeran crimson, an umber if needed and so forth depending on the circumstances. I will admit to sometimes using Payne's Grey in the sky of landscapes though.