Disclosed are a method for determining a dark condition in an image sensor to prevent a color noise and a method for interpolating colors. The present invention forms a window with a size of 5.times.5 array and determines a local color distribution based on a center pixel by using the window with the size of 5.times.5 array, thereby determining a dark condition with respect to the local color distribution. Thus, it is possible not to degrade chroma with respect to a whole image but locally degrade chroma, thereby producing a black and white image. Through differently and locally performing a color interpolation according to a dark condition determination, it is possible to correct an error of an imperfect black possibly generated during an expression of an imperfect black and white image due to the color interpolation and to reduce a color noise in the corresponding portion.