Redness
Any sight that could be roughly described as reddish or greenish is called an organic chromatic sensation. We use words like red, green, pink, chartreuse, crimson, turquoise, orange, purple, olive, scarlet, khaki, magenta etc. to identify particular visual sensations within the organic category. reports that, "No color is clearly reddish as well as greenish … redness and greenness … are mutually exclusive."1 Therefore organic visual sensations are capable of binary description. The reference experience for describing organic chromatic sensation is seeing blood.2 So to make a binary description of an organic chromatic sensation, compare it to seeing blood. Report the result using one of the following algebraic statements. If the two experiences are not comparable, then say that the sensation is not an organic chromatic sensation and express this as $\delta_{m}=0$. If the sensation is like seeing blood, then say that it is reddish. Express this as $\delta_{m}=+1$. If the sensation is not like seeing blood, then say that it is greenish and that $\delta_{m}=-1$. The number $\delta_{m}$ is called the redness.

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 Summary
 Noun Definition Organic Visual Sensation $\sf{\text{Any reddish or greenish visual sensation.}}$ 1-13
 Adjective Definition Redness $\delta_{m} \equiv \begin{cases} +1 &\sf{\text{if a visual sensation is reddish }} \\ \; \; 0 &\sf{\text{if a sensation is not reddish or greenish }} \\ -1 &\sf{\text{if a visual sensation is greenish }} \end{cases}$ 2-3
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