The only way to create black by mixing colors is to combine the primary colors together. To do this with two colors, one may use one of three combinations, hues of yellow and purple, hues of orange and blue or hues of green and red.
Creating black by mixing colors often does not result in a satisfactory shade of black. Depending on the shade and type of pigment used, results may vary. Colors would need to be mixed using trial and error, adding more or less of the pigments until a color is created that is considered to be satisfactory.