A device for generating at least blue light comprises a control circuit (4) which receives a control signal (CS) defining a variation of a spectrum of the blue light to control a photo-biological effect of a vertebrate. Therefore, first blue light (BL1) is generated with a first predominant wavelength (PW1) having a first photo-biological effect, or second blue light (BL2) is generated with both a second predominant wavelength (PW2), being shorter than the first predominant wavelength, and a third predominant wavelength (PW3), being longer than the first predominant wavelength； the second blue light (BL2) has a second photo-biological effect different from the first photo-biological effect, while the first blue light (BL1) and the second blue light (BL2) have substantially identical colors and intensities.
