Neutral colors can and will save a painting.  Neutrals are often referred to as “optical grays”.  They do not have specific names such as orange or blue, but they are created from the mixture of complement colors.

Just as complements side by side in a painting will intensify each other, mixing complementing colors will make their complement disappear.  In the disappearing stage of the mixing experience, you can take the neutral grays produced and keep them for the painting by creating values and temperatures for it.  Also, depending on the hues of the main colors and the amount of your mix, you can make many interesting colors.

Once created, the grays then can mix with white or black to create a value scale.  Add a warm color to it and the optical gray will become warm.  Add a cool color and it will become cool.

My advise is do your palette mixing in advance when it comes to your neutral grays.  Mix your warm and cool grays, and with varying values.  It will become much simpler with the grays already mixed when needed to tone down hues and chroma.

Please note the genius use of neutral colors used in Paul Cezanne’s : “Peasant in a Blue Smock” below.