Perception is the beginning of all knowledge; vision is the richest of our perceptons.  So vision is something to consider as a source of exemplars for the "higher" insights.  On this site  we start by looking at color perceptions–but also at stereopsis and  time-lapse photograpy–as routes to extensions of perceptions

This is a correct image for
Two-cone colorblindness
in the sense that every color in this picture can be specified by a set of two numbers: in this case an intensity of blue and an intensity of green.

All the colors in the PBS-TV picture that supposedly represents two-cone colorblindness can be specified by a single number that represents the intensity of blue.  That is a totally colorblind image.

Dimensionality is the key concept here.  (One of the "Six Eurekas to useful physics").
You enter the classroom on the first day of...
Click on the chick to learn how some college freshmen started their life of learning about physics.
Click here to see 
how your own vision
might fool you.
Get a large collection of paint store paint chips; they need to include a complete range of possible colors, brilliant to dull, dark to light, red thru violet, and back to red via purples.  Arrange the colors so that proximity and similarity correlate; that is, the closer together any pair of chips, the more similar they are, and the more similar, the closer together.  Any new color must fit into your arrangement.
About forty outstanding K-12 science teachers once tackled this task in small groups.  At first, none of them saw the key concept.  Even with hints not many could make a satisfactory arrangement.  None found it easy.  Dimensonality is as the edge of (easy) human comprehension.

Have you seen the key?  Then check it out... "The key," visually


Extra hints:

Vectors (and tensors)  Professors of elementary physics courses like to depict a vector as a magnitude with a direction.  That's a tad narrow.  Color is a vector; a three-vector for normal human color; a two-vector for a protanope or deuteranope.  Direction isn't involved.  Inseverability of components is the crucial issue.  Scalars can be uniquely rank ordered, just like shades of blue.  Higher order vectors (and tensors, like color reflection) cannot.  That means comparatives and superlatives are out of order.  Before you can say "A is greater than B," you must choose a scalar by which to make that ranking, and when you do you have oversimplified (infection with "the singles").  Many things are persistently and pervasively oversimplified in this way: "intelligence," "value of persons," "cost/benefit ratio," for starters.

The law of action and reaction is an observation that some certain things that might seem to be independent are, in fact, inseverable.  A movie critic once said.  "That cracking sound you hear when the movie hero punches the villain in the jaw is the sound of finger bones breaking; jaw bones are much stronger than finger bones."  That critic understood Newton's third law.  That law is recognition of implications of mutually reciprocal relationships between objects interacting with each other.  "Fairness" is a concept coming out of  the recognition of implications of mutually reciprocal relationships between people.

Sunburn and sun tan.  Actinicity of sunlight is almost universally  thought to be a function of air temperature.  Sunburn correlates with temperature; but correlation and causation are persistently and pervasively, and erroneously, thought to be the same thing.  If we note the various variables, and correctly sort through them, picking out the relevant from the irrelevant, we will come up with angle of sun from the horizon as the really relevant determiner of actinicity of sunlight.  And the relevant phenomenon of physics?  Rayleigh scattering!  Any creature with uv perception sees something humans don't.  (That goes for polarization perception, too.)