Trouble darkening when painting with yellow
To darken the tone when painting with yellow, if you add grey, often your mix will start to look slightly green. To stop this from happening, Anna selects the complementary colour from the colour wheel, which is Cobalt Violet. When combined, complementary colours will balance each other out to create a more neutral tint, so it is a good idea to become familiar with the Munsell colour wheel.
Click on this link to see Anna's blog on how to paint shadows when using yellow.
Munsell's Colour Wheel