A couple weeks ago I had a flock of cranes land in front of me at the Rocky Weed pothole. I'd never noticed variable they are in spring (maybe fall too? I've never gone to one of the migration roosts).
I'm not sure how much this is a matter of age and how much it's geographic. Sibley summarizes variation in this species with Greater (southern) and Lesser (northern) Sandhills with intermediate populations as well. Even the southern cranes extend to Canada for their breeding. Pyle and the Nat Geo allude to about 4 or 5 subspecies. The Lessers have a lot more dark in the wings.
One of the birds was noticeably smaller and darker.
The birds took flight after a few minutes though.