https://venn.bio-spring.top/intro#nvennr

In popular terminology they are very often confused with Euler Diagrams [0] which represent meaningful relations in sets but not all possible. You shouldn't create Euler Diagrams this complex, but the raison d'etre of Venn diagrams is to visualize the complex nature of set relations.

0. https://en.wikipedia.org/wiki/Euler_diagram

https://bombmanual.com/web/index.html#ComplicatedWires

However you could make a good argument that having a complicated and confusing diagram is the point of that puzzle.

I was in a genetics graduate program when this was published, and this spread like wildfire.

The author's mistake was this: "[my colors] are equidistant in the hue circle". The problem is that the hue circle (at least under the parameterization scheme he used) is not uniform over discrimination, i.e., the ability to discriminate two hues is not invariant under displacing them an equal amount along the circle. (I presume this is one of those situation where it's misleading to think about three primary colors on equal footing because of quirks of human vision biology.)

First, the author could have chosen 7 hues at max-saturation that were easier to discriminate than this. But more importantly, he should have used the other color axes: saturation and brightness. dark red (~maroon) and light red (~pink) are a lot easier to discriminate, even when not next to each other, than the two shades of green he used.