An illumination system has a mounting substrate (4) for mounting and electrically contacting a plurality of light-emitting diodes (R, A, G, B). A first category of the light-emitting diodes (G, B) comprises a first translucent substrate (11) provided with an active layer (1) on an outer surface (13) of the first translucent substrate facing the mounting substrate (4); electrical contacts are provided at a side facing the mounting substrate. A second category of the light-emitting diodes (R, A) comprises an active layer (2) arranged on a second translucent substrate (12); at least one electrical contact is provided at a side facing away from the mounting substrate. Each light-emitting diode of the first category is provided on a first sub mount (21). Each light-emitting diode of the second category is provided on a second sub mount (22). The first and second sub mount are provided on the mounting substrate.