The manufacturing process of LEDs results in a discrepancy in the radiated colours. Therefore, manufacturers categorize LEDs with similar colours and similar brightness in the so-called binning classes. If the class is large enough, colour differences in the final product might be noticeable and, as a result, influence strongly the customer's appreciation. To evaluate the resulting colour discrepancy of a system, different methods using both full-filtering and partial filtering spectral measurements are combined with integrated/angular spectral measurements provide the chromaticity coordinates. Measurement tolerances are derived from these basic measurements. Taking the tolerances into account, the real colour binning class increases. The measurement tolerances of different LED manufactures vary in the range of δxy = 0,005 - 0,012. This paper shows the results to the topic maximum acceptable size of the LED's binning classes in combination with a light-guide comprising both primary and secondary optics (BMW DRL Rings) at a luminance level of a position lamp. This was realized using a lit appearance simulator. The results can be used for the development process to further improve the quality and the design of automotive light functions. In addition, the simulator of lit appearance facilitates the visual percipience of a LED colour binning before the development of a prototype. Thus, time and money can be saved. So far the results of the study and experience gained within the development process have shown that within LED binning classes of different manufacturers colour dispersion can be clearly perceived. Hence, manufacturers should reconsider their classifications and reduces their binning classes. In addition, measurement tolerances should be included into the binning parametres by the manufacturer.