1. A method for color feature extraction, adopted to extract color feature from an image signal, comprising the steps of: (A) receiving the image signal including plural image pixels, each image pixel having a color; (B) mapping the image signal to a color space model, enabling the color contained by each of the plural image pixels to be respectively mapped to a corresponding point in the color space model, the corresponding point having a coordinate represented by a first parameter, a second parameter, and a third parameter, the color space model including a color plane composed of plural color regions and plural fuzzy regions; (C) comparing the third parameter with an adjustment threshold value to have a comparison result, and obtaining an adjusted second parameter based on the comparison result and the second parameter; (D) sequentially clustering each of the color provided by the plural image pixels into one of the plural color regions or one of the plural fuzzy regions of the color plane according to the first parameter and the adjusted second parameter; and (E) designating a color feature vector to each of the plural image pixels according to a result of clustering.