True color blindness (as opposed to "social" color blindness) does not apply only to race. It also applies to origin, social status, appearance, gender, height, dress fashion, music, sexual preference, and virtually everything else that matters to human beings.
The Truly Color Blind (TCB) person understands spoken language on a practical level.
Look at the following two sentences:
1. Would you be so kind as to pass the bread, please?
2. Gimme bread (or, simply, Bread!)
Granted, the first sentence is much more polite. The second one may be irritating, but a truly color blind person will not be irritated. As long as he has established a channel of communication with his interlocutor he won't notice the difference between the two sentences, because he has conditioned himself to extract the essential from what he hears. And the essential in both sentences is that the speaker wants bread. You have the bread and he's asking you to give it to him. That's all there is to it and any further analysis is pointless and harmful.
Try to picture you and your teenager son sitting at the breakfast table. Suddenly he says: "Would you be so kind as to pass the bread, please?" You'd certainly think that he was either sick, or mocking you. Conversely, if he were to say "Bread!" with his mouth full, you would pass it to him and go on reading the newspaper, unruffled. That is because your levels of trust and of communication with your son are such that you are able to perceive his signals without attaching any sinister significance to the way he conveys them. True, you’d rather have him express himself more articulately and civilly, but that belongs to the domain of education; you'll perhaps try to teach him, for his own good, not because his behavior was offensive to you but because you are afraid that it may be offensive to other people, who may not know him as well as you do.
A truly color blind person is one who is conditioned to see and hear the essence of a sentence and to pay no attention to the rest, in what turns out to be an economic and efficient process. Returning to our example, in the first sentence the TCB person hears all the words but only processes those that matter. He files "Would you be so kind as to" away as non-operative words, along with "please". Now he is left with "pass the bread", which sounds pretty much like simply "bread".
Let's look at another example. Two people speaking different languages have lunch together. They can’t converse, because they don’t understand one another, so they resort to signs. They both know that whatever meaning the other tries to convey must be interpreted taking into account the inherent difficulty they have in communicating. Now one points to the bread basket and then to himself. The other understands and obliges by passing the bread. This exchange is exactly the same as saying "gimme bread!", but nobody would ever think that the person who asked for bread was being rude. Why is that so? Because anybody can appreciate that under the circumstances communication on the barely essential level was a necessity. One cannot say "would you please" by pointing with his finger (although one could do it by adding a smile.)
On the basis of the above examples we can enunciate one of the most important principles of true color blindness: Always look for the essential meaning of the message. Once you have done so, you are free to process the rest of the information without it getting in the way of understanding your interlocutor's intention.
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Where do you draw the line between efficient speech and rudeness?