We also assessed the light spectrum from the digital light projector and found that at full intensity it contained peaks at 460 nm, 510 nm and 640 nm corresponding to the red, green and blue (RGB) LEDs within the projector (Figure \ref{954344}). Little overlap was observed between each of the LEDs’ emission spectra (<2%) making them suitable for multiplexed communication to individual agents (i.e. using each colour as a separate channel).