Question: which of the following are examples of primary sources (select all that apply)

title: Primary color
text: A contemporary description of the color vision system provides an understanding of primary colors that is consistent with modern color science . The human eye normally contains only three types of color photoreceptors , known as long - wavelength ( L ) , medium - wavelength ( M ) , and short - wavelength ( S ) cone cells . These photoreceptor types respond to different degrees across visible electromagnetic spectrum . The S cone response is generally assumed to be negligible at long wavelengths greater than about 560 nm while the L and M cones respond across the entire visible spectrum . The LMS primaries are imaginary since there is no visible wavelength that stimulates only one type of cone ( i.e. , humans can not normally see a color that corresponds to pure L , M or S stimulation ) . The LMS primaries are complete since every visible color can be mapped to a triplet specifying the coordinates in LMS color space . Normalized