In many color models, there is an axis for achromatic colors that lies between the black and white values. On this achromatic or brightness axis are the gray levels between white and black. Depending on the resolution, this can be '2^8' or more shades of gray.
Uncolored colors are also called achromatic, which means "without color information". Depending on the color mixing, the achromatic values can be composed of the addition of the three primary colorsred, green and blue, or of the subtraction of cyan, magenta and yellow.