I have for some time omitted black from my palette and have depended on mixing blacks and grays using complements or near complements. My favorite combinations to date have been 1) ultramarine blue and burnt sienna and 2) (when I have green on my palette) Thalo green and alizarin crimson. I have so far not found a combination on the yellow-purple complement that I care for as "black" (although I've gotten some good muddy colors), but I assume that I just haven’t found the correct combination. Yellow is so light a value that any combination with purple that gets close to neutral tends to be too light for a rich black. This could probably be remedied by selecting one of the dark yellow neutrals such as raw sienna or yellow ochre rather than high-hue yellow.
By the way, a student asked me the other day if I was familiar with “Payne’s Grey” so — curious as to what its mineral components were — I looked it up. It turns out that (according to Wikipedia) Payne’s Grey is simply a mixture of burnt sienna and ultramarine blue. So now you don’t need to go out and buy Payne’s grey.
But I wrote a poem with a Payne’s grey sky in it some time ago, and I include it here:
It’s a Payne’s grey watercolor sky,
blotted clouds grumbling in anticipation.
Somewhere it’s started to rain.
I will weep, weep with the rain
which hurricanes my heart’s ache
descending in typhoons.
Strong trees may break
before this is over.
It is a long slow rain,
flooding the path to the house.
In a distant land, men are fighting.
I will weep with the rain
Exercise: If you have old tubes of paint lying around or you don’t mind the expense of trying new colors, here are some possible colors to try mixing for blacks and greys. A familiarity with and ability to mix various blacks and grays will give your paintings more richness.
1) alizarin crimson and thalo green. (Also try any magenta or cool red with assortment of greens.)
2) cadmium orange and cobalt blue. (Also try other orange and blue combinations. Try also blues with warm browns – which are actually dull oranges.)
3) Indian yellow and dioxazine purple. (Also try raw sienna and other yellow-browns with purples.)