Try what I do.
for glazing over white technique..raw umber, burnt umber, burnt sienna, sap green, yellow ochre, thats it. glaze green over brown to cool it and vice versa. for warm reds and yellows. glaze the brown and ochre
for opaque. limited palette. mars black, cadmium red medium hue, yellow ochre, white.,,,,greens are ochre and black. for the face.
for every painting you do, you will either be mixing the correct value and tint for the strokes or area you need, or you will make note of the tints you will need, as recipes for your scene. some complimentary color scheme like purple versus yellow, etc. dull all your colors down with a little brown.
The greatest masters, Old Masters, premixed all of their colors with a limited palette.
try painting with sun thickened linseed oil to keep your paint from getting muddy. Masters used it.
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