Silas: red is not the set, but what all of those things have in common. The set would be most effective if you presented a sequence of examples that was different in every way except in color. To be extra sure of getting the point across, you could present examples that are exactly the same, except in color, and then say one was “red” and the other was “not red”—a whole educational philosophy has been built up out of this (look up Siegfried Engelmann and Direct Instruction). Of course this method of communication assumes that the audience is sighted, not colorblind, understands the concept of “same” and “different”, etc.
Silas: red is not the set, but what all of those things have in common. The set would be most effective if you presented a sequence of examples that was different in every way except in color. To be extra sure of getting the point across, you could present examples that are exactly the same, except in color, and then say one was “red” and the other was “not red”—a whole educational philosophy has been built up out of this (look up Siegfried Engelmann and Direct Instruction). Of course this method of communication assumes that the audience is sighted, not colorblind, understands the concept of “same” and “different”, etc.