1. An instrument to identify the colors for an image, the image having one or more elements, each element having a color the instrument comprising: a plurality of sensors; a filter; and means for moving the filter so that the filter can be positioned in between the sensors and the image; such that the instrument is capable of generating at least three output values to measure the color of each element; the colors of the image are measured sequentially at least twice, once with and once without the filter in between the image and the sensors, to identify the color of each element of the image; and wherein the filter is selected by the steps of: picking a filter from a plurality of pre-selected filters for the instrument; identifying the colors of a plurality of pre-selected images by the instrument, the color of each pre-selected image being known and different from the other pre-selected images; calculating a difference value based on the difference between the identified color and the known color of each pre-selected image; repeating the step of "picking a filter" until every pre-selected filter has been picked; and selecting the filter that provides the minimal difference value.