Nature's yellow and black

I think nature mixes yellow with almost every one of  her  hues,  never,  or  very  rarely,  using  red without  it,  but  frequently  using  yellow  with scarcely  and  red;  and  I  believe  it  will  be  in consequence found that her favourite opposition, that which generally characterizes and gives tone to  her  colour,  is  yellow  and  black,  passing,  as  it  retires,  into white and blue. It is beyond dispute that the great fundamental opposition  of  Rubens  is  yellow  and  black;  and,  that  on  this, concentrated in one part of the picture, and modified in various greys  throughout,  chiefly  depend  the  tones  of  all  his  finest works. And in Titian, though there is a far greater tendency to the purple than in Rubens, I believe no red is ever mixed with the
pure  blue,  or  glazed  over  it, which  has  not  in  it  a  modifying quantity  of  yellow.