the same woman and girls in that iconic Depression-era photograph?-
I don’t think so, nose and ears aren’t a good match. Funny how that bob style haircut is still popular for kids today.
The color photo is ID’s by the Denver Post as “Jack Whinery, homesteader, and his family. Pie Town, New Mexico, October 1940”.
Your BW lady is Florence Owens Thompson of Nipomo, CA, photographed by Dorothea Lange in 1936, and given the title “Migrant Mother”.
More information and a drawing based on another photo in the series at http://www.flickr.com/photos/texaslady_50/3571320365/