Abstract: A method and an apparatus for simulating a visual surface pattern of a fiber product and a method and an apparatus for producing a multicolored BCF yarn. In this case, at least one parameter of a strand-like fiber bundle is sensed and is digitized into data which is converted with the aid of evaluation electronics into a surface pattern. The visual appearance of a longitudinal portion of the fiber bundle may be detected as an image as a parameter of the stand-like fiber bundle. A rapid and reproducible simulation of the visual surface pattern of a fiber product is consequently possible. Additionally, the production of the fiber product, for example a BCF yarn, can be monitored by means of the simulation results, so that at least one process parameter can be selected and/or monitored. For this purpose, an image acquisition appliance is provided, which is assigned to a bobbin or to the BCF yarn and which is connected to an evaluation device for an actual-value/desired-value comparison.