A device comprising: a power supply ; a first light emitting device for generating light of a first color; and a boost converter having an input node electrically coupled to the power supply and having an output node, with the first light emitting device electrically coupled between the output node and a first reference node to receive a continuous electrical current from the boost converter, wherein the boost converter comprises, a switch (S) electrically coupled in a current shunting path between the input node and the first reference node , wherein the switch (S) is configured to shunt current from the power supply around the first light emitting device , and a controller configured to generate a pulse width modulation (PWM) signal to control a duty cycle of the switch (S) to provide a pulse width modulated, PWM, electrical current through the switch (S) and the continuous electrical current through the first light emitting device ; and characterised by a second light emitting device for generating light of a second color, different to the first color, electrically coupled between the input node and the power supply and/or between the first reference node and a second reference node, so that a current through the second light emitting device is equal to a sum of the pulse width modulated electrical current through the switch (S) and the continuous electrical current through the first light emitting device . a power supply ; a first light emitting device for generating light of a first color; and a boost converter having an input node electrically coupled to the power supply and having an output node, with the first light emitting device electrically coupled between the output node and a first reference node to receive a continuous electrical current from the boost converter, wherein the boost converter comprises, a switch (S) electrically coupled in a current shunting path between the input node and the first reference node , wherein the switch (S) is configured to shunt current from the power supply around the first light emitting device , and a controller configured to generate a pulse width modulation (PWM) signal to control a duty cycle of the switch (S) to provide a pulse width modulated, PWM, electrical current through the switch (S) and the continuous electrical current through the first light emitting device ; and a switch (S) electrically coupled in a current shunting path between the input node and the first reference node , wherein the switch (S) is configured to shunt current from the power supply around the first light emitting device , and a controller configured to generate a pulse width modulation (PWM) signal to control a duty cycle of the switch (S) to provide a pulse width modulated, PWM, electrical current through the switch (S) and the continuous electrical current through the first light emitting device ; and characterised by a second light emitting device for generating light of a second color, different to the first color, electrically coupled between the input node and the power supply and/or between the first reference node and a second reference node, so that a current through the second light emitting device is equal to a sum of the pulse width modulated electrical current through the switch (S) and the continuous electrical current through the first light emitting device . <EOS>