Opposite colors mix to make a neutral dark.  This combination of primary and secondary oppositions naturally makes a perfect Black or Gray of any shade. Magenta and Green is the perfect afternoon opposition, it can make either a warm or cool shadow for Green or Magenta.

Thalo Green now comes in Thalo Green Blue/Side, Thalo Green and Thalo Green Yellow/Side.
Danial Smith makes the best Quinacridone Magenta hue on the market. It is essential for a limited palette, any palette for that matter.