If we could get that to work, then we'd be much closer to VR without a headset - a device able to paint arbitrary images directly onto users' retinas could be stationary and handle multiple users - giving us a holodeck, just without the tactile parts.
"This is a good time to spare a thought for our red-green colorblind brethren. [...] it is to them that we owe the beautiful color of green traffic lights. The spectral requirements that make the green signals distinguishable from red in their eyes make them beautiful in ours."