@Azriel4444;
Red and Green are used for a very good reason, in that the human eye focuses red and green light differently due to their different wavelengths and position on the visual spectrum. Even if you can't clearly see red and green, they will still appear differently to you and the test will still work.
In any event, this is a nifty gimmick in terms of portability, but brings nothing new to the table in real terms. It's simply a mobile way to do refraction estimates, so replaces an autorefractor unit, which is routinely used in Optometry, and only really provides an estimate of the final prescription. Nobody in their right mind would want to prescribe from the results of this only.