Colour point control system (1) comprising a LED device (2) comprising a plurality of light-emitting diodes (3a,3b,3c,3d) emitting a first light, said diodes (3a,3b,3c,3d) fixed on a substrate (4), a layer (5) on at least one light-emitting diode (3a,3b,3c,3d) capable to convert at least a first portion of the first light into a second light, only one photo-sensor (6) for measuring a second portion of the first light of each single diode (3a,3b,3c,3d) during a turn-off time where all other diodes are turned-off, and a controller (9) for sequentially turning-off said diodes (3a,3b,3c,3d) except one single diode (3a, 3b, 3c, 3d) and for comparing the second portion of the first light of each single diode (3a,3b,3c,3d) measured by the photo-detector (6) to a default value and to adapt the emitted second portion of first light of each single diode (3a,3b,3c,3d) to said default value.