The colors of the buttons/circles indicates privacy levels. Ancestors over 200 yrs are open to everyone, whereas RED indicates living persons and only the profile manager and the trusted list can see the details. Other colors indicate differences in what the public can view.
Key:
The colored dots are the Privacy Level: Unlisted , Private , Private with Public Biography , Private with Public Bio and Tree , Public , or Open .
See more details at:
http://www.wikitree.com/wiki/Privacy
I did note that some that are white, are not clickable from that page, however if you type them in the Surname box, you do get to the page for that person, such as
GADDAH (1 - Frances Gaddah) is not clickable but when you type Gaddah in the surname search you get: Frances Gaddah 1718 Bedford, Virginia, United States
So someone else will have to explain that.
Thanks for supplying that link, made a lot more sense!