The ability to provide very high data rates is a significant benefit of optical wireless communication (OWC) systems. In this paper, an optical wireless downlink in a data centre that uses wavelength division multiple access (WDMA) is designed. Red, yellow, green and blue (RYGB) laser diodes (LDs) are used as transmitters to provide a high modulation bandwidth. A WDMA scheme based on RYGB LDs is used to provide communication for multiple racks at the same time from the same light unit. Two types of optical receivers are examined in this study; an angle diversity receiver (ADR) with three branches and a 10 pixel imaging receiver (ImR). The proposed data centre achieves high data rates with a higher signal-to-interference-plus-noise ratio (SINR) for each rack while using simple on-off-keying (OOK) modulation.