According to one hypothesis, the hypertensive effect of alcohol is from a chronic state of alcohol withdrawal in frequent, heavy drinkers, but there is much evidence in favor of a direct effect of alcohol on BP.
Color Perception. The properties of color which are inherently distinguishable by the human eye are hue, saturation, and brightness. While we know that the spectral colors can be one-to-one correlated with light wavelength, the perception of light with multiple wavelengths is more complicated. It is found that many different combinations of light wavelengths can produce the same perception of color. This can be put in perspective with the CIE chromaticity diagram. The white or achromatic point E can also be achieved with many different mixtures of light, e.g. with complementary colors.
Since visual perception is one of the most important species of perception and hence of our acquisition of knowledge of the physical world, and of our environment, including our own bodies, a theory of color is doubly important.