The method 2, wherein said step of detecting the intermediate value of each color includes dividing the total number of colors capable of being expressed by said red, green and blue colors into 256 gradations, and selecting {TAIL ~ intermediate colors} with respect to {HEAD ~ the colors} which are divided into 256 gradations 
The method 2 , wherein said step of detecting the intermediate value of each color includes dividing the total number of colors capable of being expressed by said red , green and blue colors into 256 gradations , and selecting { TAIL ~ intermediate colors } with respect to { HEAD ~ the colors } which are divided into 256 gradations
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