Most colors in the natural world are neutralised to a lesser or greater extent. The blue of the sea is almost never the shade of pure ultramarine straight from a tube. Another word for neutral is grey. When complementary colors are mixed together in equal amounts, they produce grey. This is the key to natural colors exploited by the Impressionists. To gain a natural look to colors try adding small amounts of it’s complementary color. This will produce the appropriate chroma, and take away that garish look that is easy to get when painting. On the other hand, neutralising colors too much gives a muddy look. It needs to be done with subtlety.