Two different theories exist for color mixing. The additive color mixing theory refers to the mixing of light. In additive color mixing the primary colors used in mixing are blue, red, and green. When all three primary light colors mix white light is presented, making white the existence of all colors and black the lack of light colors. Additive color mixing is used on computer and television screens.
In painting applications the theory of color mixing that is used is the theory of subtractive color mixing. In subtractive color mixing the primary colors are blue, yellow, and red. When all three primary color pigments are mixed together black is formed, making black the presence of all colors and white the absence of color in the subtractive color mixing theory.
In the additive theory of color mixing green and red are mixed to make yellow shades, blue and green create a bright, light blue, and red and blue create a color called fuchsia. To create dark blues, light blue, light reds, light greens, pale yellows, and any other shade variation of a color white and black light cannot be added; rather variations on the amount of red, green, and blue light must be adjusted to make the necessary colors.
To create secondary colors using the subtractive color mixing theory, which is used extensively in painting, the three primary colors are mixed in equal parts. True secondary colors will exist as equal parts of two of the primary colors mixed. When equal parts of blue and yellow are mixed, green will result; blue and red will make purple, and red and yellow will create orange. If equal parts of the primary colors are not mixed, a tertiary color will form a tertiary color is a mix of color that has more of the color value of one of the primary colors used in mixing. Red-orange, yellow-green, and blue-violet are examples of tertiary colors.
In the subtractive color mixing theory white and black pigments are used to make various shades of different primary, secondary, and tertiary colors. When white is added to a color a lighter shade of the color is produced upon mixing, and when black is mixed with a color a darker shade of the color is produced.