An apparatus in which the concentration of toner particles used to form a highlight color document is controlled. The percentage of the document arranged to have highlight color portions thereon is determined and a first signal corresponding thereto generated. A second signal corresponding to the rate of toner particle usage per document is transmitted. A third signal corresponding to the total number of documents being reproduced is produced. The first, second and third signals are multiplied to generate a control signal corresponding to the required dispense rate for the toner particles forming the highlight color portions of the document.