1. A false contour reduction device, which reduces an occurrence of a false contour on a display screen of a display device, comprising: a false contour reducing unit for performing a false contour reducing process on a specific color false-contour-generating image signal, wherein the specific color false-contour-generating image signal comprises an image signal which comprises a false-contour-generating image signal and which has a specific color in a specific color range among input image signals, wherein the false-contour-generating image signal comprises an image signal which will generate a false contour, wherein the false contour reduction device further comprises: a false-contour-generating image signal detector for detecting the false-contour-generating image signal among the input image signals; and a specific color false-contour-generating image signal detector for detecting the specific color false-contour-generating image signal among the false-contour-generating image signal detected by the false-contour-generating image signal detector, wherein the false contour reducing unit performs a first false contour reducing process on the specific color false-contour-generating image signal detected by the specific color false-contour-generating image signal detector, wherein the false-contour-generating image signal detector determines that the input image signals comprise the false-contour-generating image signal when at least one color image signal among a plurality of color image signals in the input image signals falls within a predetermined gradation range and a pixel corresponding to such color image signal continuously exists over a predetermined area on the display screen in a single frame, wherein the false contour reduction device further comprises a first through mth field delay units located between the specific color false-contour generating image signal detector and the false contour reduction unit for delaying, by one through m fields, introduction of the specific color false-contour-generating image signal to the false contour reducing unit, wherein the false contour reducing unit also performs at least a second false contour reducing process when the specific color false-contour-generating image signal is introduced to the false contour reducing unit from at least one of the first through mth field delay units, on a subsequent input image signal which is introduced to the false contour reducing unit later than the specific color false-contour-generating image signal and which is used in the display device at a same display screen location as the specific color false-contour-generating image signal, even if said subsequent input image signal is not the false-contour-generating image signal, and wherein, whether said at least the second false contour reducing process is performed is decided based on a detection result on a preceding image signal by the false-contour-generating image signal detector.