This is a case series testing the feasibility of using bioelectronic retinal prostheses to partially restore colour perception in seven patients with advanced retinitis pigmentosa. Bioelectronic retinal prostheses are able to bypass degenerated photoreceptors to directly stimulate the inner retinal neurones. The authors tested frequency-modulated electrical stimulation of the retina. The primary outcome was to measure the perceived brightness and colour of the subjects that was elicited through electrical stimulation. The study found that five out of seven subjects were able to perceive chromatic colours along or nearby the blue-yellow axis in colour space, with an increase in stimulation frequency (6-120 Hz) being able to shift the colour perception into the blue-purple range. The authors raise the issue of current uncertainty with regards to tissue damage upon prolonged high frequency stimulation. As such, further research is required on the feasibility, safety and clinical utility of this technology.