That still doesn't make sense. They're not saying one time is genetic and the other time is not genetic. I think youre misinterpreting what they're saying.

He said "we don't really know why every time, Its partly genetic luck".

The key words are "every time" and "partly"

Perhaps saying "interprets" rather than "fills in" is more accurate when talking about colours. Either way the brain processes that information and what we "see"is the result. Also I think it's cones that are more to do with colour rather than rods so I got mixed up with that.

The brain and how it perceives colours is an interesting thing. Take magenta for example, in reality that colour doesn't exist but it's our brains filling it un to make sense for us. Also the colour yellow is seen by everyone differently as our eyes only have red, blue and green rods so it takes information from the green and red cones and fills in the blanks. I'm sure I read somewhere that goldfish have yellow rods un their eyes so can truly see what the colour yellow us. Also look up about impossible colours, it's fascinating what our brains do and how we perceive what we "see" is just the brains interpretation of data/information.