Hue
Hue is what is often more generally called "color." It is the characteristic color of light at a particular wavelength. For example, light with a wavelength of 475 nm is blue. We perceive color by how the color sensing organs in the eye, called cones, are stimulated by different wavelengths of light. White and black are not hues, but the presence or absence of all hues together. For pigments, adding white or black changes the color, but the hue remains the same.
The pure hues of the visible spectrum are not the only possible colors. Colors can be formally specified in terms of a color model, of which there are many. A color space includes all the colors that can be defined for a particular color model. The Commission Internationale de l'Eclairage (International Commission on Illumination) L*a*b color model is generally recognized as the most accurate method of describing colors visible to the human eye.
Maximum 12 points
All the items in this section and the next (Color Schemes) recieved full points. The definitions are fairly straightforward but the discussion took some thought. I chose to discuss technical points of color perception rather than any interpretation of what colors "mean" because it is so subjective. From a physical standpoint, there is no such thing as color the way an object has mass or shape.