Having recently heard about someone who was refused a place at medical school due only to his colour blindness, I began thinking of ways to help those of us with an impoverished ability to distinguish between eg shades of red and green (which affects hue discrimination in 5% of all males).
Rather than use (expensive) coloured contact lenses, simply equip colour blind people with a bright pencil torch, over which is fitted a coloured filter. For red/green deficit, the filter could be red so that when viewing a scene containing both red and green items, the red ones would stand out more brightly. The torch could be incorporated into eg spectacle frames for added discretion and also for driving (who thought that making traffic lights red and green was a good idea?)
These days it is possible, given some clever correction for background lighting, to undertake analysis of a digitised scene and to create an ‘augmented reality’ by applying eg a sparkly texture to regions which a normally sighted person would describe as ‘red’. Even a crude version of this, which was able to detect any red and green patches lying close enough together in a scene, could be used to provide an alert.