White objects reflect all wavelength of light and in contrast, no pun intended, black objects absorb all wavelengths. Our perception is not always reality. Degrees of color blindness exist, i.e. inability to distinguish blue from green. Some people also have highly sensitive color perception, allowing visual differences to be detected that the sensory tester may not see. Consistent responses about an object color are often given by subjects even when filters are used to mask differences.
Perception of color is influenced by background and relative sizes of contrasting color.
The texture and gloss of a surface can also affect perception of color in sensory testing.