This website offers age progression photographs.
http://www.phojoe.com/
They say that they took what pictures the could find of DannieLynn and did a age progression photo with those pictures.
After they got done they put the age progression picture up next to each of the suspected fathers and DannieLynn's age progression picture matched up best with Birkhead's. The picture below is a digital picture I took of my TV showing the DannieLynn age progression sitting next to a picture of Birkhead.
I am not sure why they gave her blond hair because Anna & Birkhead are not natural blonds - but maybe they figured at the age of 18 that DannieLynn may bleach her hair like her mother did.