1. A method for determining color value of a pixel for an image processing operation, comprising steps of: providing a reference depth value representing a level of motion of the pixel; providing a plurality of color values and corresponding depth values of the pixel at a plurality of levels of motion; and selecting a target color value of the pixel among the plurality of color values according to the reference depth value and the plurality of depth values; wherein the reference depth value is obtained by the following steps: receiving color values of the pixel in a first field, a second field and a third field respectively, wherein the first field is preceding to the second field and the third field is next to the second field; and determining the reference depth value according to the color values of the pixel in the first field and the third field; and wherein the plurality of color values correspond to M different levels of motion, the plurality of color values and corresponding depth values Z are determined as: setting the color value of the pixel to f(n−1) and the depth value Z=Z 1 at a level of motion Ll; setting the color value of the pixel to [((a−1)/(M−1))xf(n)+((M−1)−(a−1)/(M−1))xf(n−1)] and the depth value Z=Za at a level of motion La; and setting color value of the pixel to f(n) and depth value Z=ZM at a level of motion LM; wherein the color value of the pixel in the first field is f(n−1), the color data of the pixel in the second field is f(n), 1<a <M, and Z is the depth value of the pixel with Zl<Za<ZM.