Your diagram is not a valid diagram. The purpose of venn diagram is to show sets, their intersection, relations, etc. Yours did none of this, it was a blob of color.
The reason I softened them was to show that all persons who are citizens by birth appeared to be "natural born citizens" for the purpose of Article II eligibility.
That, and it makes the text easier to read.
If I were doing it over, the only thing I would change would be upping the confidence level even more that children born citizens to US citizens overseas are natural born citizens as well.
It is an accurate representation of our history and the law.
That, and I might clarify that those in the overlap are born in the US to citizen parents.