1. A computer-implemented method for modifying a depth map of a two-dimensional color image for enhancing a 3D image rendered therefrom, comprising: A) obtaining a first color image and a depth map associated therewith containing depth values for pixels of the first color image; B) displaying at least one of the first color image and the depth map on a computer display; C) selecting a depth adjustment region (DAR) in the depth map for modifying depth values therein by performing the steps of: a) receiving a first user input identifying a first pixel color within a range of colors of a target region in the first color image; b) upon receiving a second user input defining a pixel selection rule for selecting like-coloured pixels based on the first pixel color, using said pixel selection rule for identifying a plurality of the like-coloured pixels in the first color image; c) displaying a region visualization image (RVI) representing pixel locations of the plurality of like-coloured pixels; d) repeating steps (b) and (c) to display a plurality of different region visualization images corresponding to a plurality of different pixel selection rules for selection by a user; and e) identifying a region in the depth map corresponding to a user selected region visualization image from the plurality of different region visualization images, and adopting said region in the depth map as the DAR; D) generating a modified depth map by modifying the depth values in the DAR using a selected depth modification rule.