Method for detecting a dot of functional material on a medium on a predetermined location, the dot having a predetermined colour, wherein the method comprises the steps of a) determining an environment of the predetermined location, comprising a plurality of pixels surrounding the predetermined location and including the predetermined location itself, b) scanning the environment resulting in scanning values for each pixel of the environment, and c) for each pixel of the environment establishing a value for a lightness component of a colour of the pixel derived from the scanning values, d) for each pixel of the environment establishing a chroma value for a chroma component of a colour of the pixel derived from the scanning values, e) summarizing the chroma values of the pixels of the environment into a summarized chroma value for the environment, f) summarizing the lightness values of the pixels of the environment into a summarized lightness value for the environment, g) comparing the summarized chroma value to a predetermined chroma threshold value for the predetermined colour of the dot, h) comparing the summarized lightness value to a predetermined lightness threshold value for the predetermined colour of the dot, i) deciding whether or not the dot is present in the environment based on both comparing steps, and j) for each pixel of the environment establishing a hue value for a hue component of a colour of the pixel derived from the scanning values, and only chroma values of the pixels of the environment are summarized in step e) which pixels have a hue value for the hue component of the colour of the pixel within a predetermined hue angle range for the predetermined colour of the dot, wherein the dot is part of a background spit pattern designed with respect to detection of a failure of a printing element in a colour image reproduction apparatus, said printing element suitable to eject the dot. a) determining an environment of the predetermined location, comprising a plurality of pixels surrounding the predetermined location and including the predetermined location itself, b) scanning the environment resulting in scanning values for each pixel of the environment, and c) for each pixel of the environment establishing a value for a lightness component of a colour of the pixel derived from the scanning values, d) for each pixel of the environment establishing a chroma value for a chroma component of a colour of the pixel derived from the scanning values, e) summarizing the chroma values of the pixels of the environment into a summarized chroma value for the environment, f) summarizing the lightness values of the pixels of the environment into a summarized lightness value for the environment, g) comparing the summarized chroma value to a predetermined chroma threshold value for the predetermined colour of the dot, h) comparing the summarized lightness value to a predetermined lightness threshold value for the predetermined colour of the dot, i) deciding whether or not the dot is present in the environment based on both comparing steps, and j) for each pixel of the environment establishing a hue value for a hue component of a colour of the pixel derived from the scanning values, and only chroma values of the pixels of the environment are summarized in step e) which pixels have a hue value for the hue component of the colour of the pixel within a predetermined hue angle range for the predetermined colour of the dot,