There is no such thing as local color, which is an idea of color based on a name (red, blue).
OPTICAL COLOR treats color as a function of lighting conditions and adjacent colors, rather than an unchanging attribute of an object. Optical color choices are based on how the subject appears under specific lighting conditions, rather than what the artist knows is the local color. Using optical color means acknowledging that conditions such as lighting and proximity to other colors alter the perception of local color. The color you perceive often has little relation to the local color.
ARBITRARY COLOR is not based on observation, but is used for expressive or decorative purposes.
Search for the particular, specific color as it appears before your eyes. Any old version of red or blue won't do. AVOID APPROXIMATION. Aim to get it right the first time. Don't put something approximate down with the idea that you will go back to it later. With this approach, if all goes well, the first step will be the last step.
Try to forget that you are looking at a leg, or a pumpkin, or whatever it is. Forget the name of it, forget what you think the color should be. Forget rendering smoothly or making something "realistic." Think shape, specific color, relative value. Those three things will give you plenty to work with. If you get those things right, you won't need anything else. If you get them wrong, no amount of detail will make the painting live.
NEUTRAL. This word is almost as confusing (and meaningless) as "local color." When I say neutral, I mean neither warm nor cool. There are all kinds of browns, tans, putty colors that are often called neutral, but they can be very yellow or green, red or blue (warm or cool). There are many ways to arrive at a neutral gray. Mixing two complementary colors together is a place to start. You will need to experiment with amounts of each complementary color. What happens when you mix them 50/50? What happens when you mix them 25/75? What happens when you add white? If your result is too warm or too cool, which third color should you introduce to get the color you are aiming for? In what amount?
Make no assumptions about what will happen when you mix one color with another. Even when you mix the same two colors, with the same two names, of different brands, the results can be dramatically different.
There are no prescriptions that can be relied upon to yield the same results each time. There are too many variables.
Knowledge of how colors behave when mixed has to be derived from experience. It is achieved by covering hundreds of square miles of canvas.
10,000 hours at the easel with a brush in your hand is a start.
