The Primary colors are defined as those that cannot be mixed from other colors.
They are: Red, Yellow, and Blue.
You may have hear of other systems of primary colors such as CMYK, or other systems of color mixing such as additive colors. CMYK is used in film and print. Additive color is used for lighting, computer displays, any place where color is being emitted.
We will be focusing on subtractive color, as used in painting.
We have seen why this is called subtractive color, in the section on how colors get their color, and we will see even more in the color mixing sections.