You can see marbling in a 2 inch juvenile if you know what to look for. But the really nice marbling can start at only 3 or 4 inches. Depends on the individual and the genetics. One of the females I used to have would produce very marbled young on a regular basis—but she has none herself.
Awesome story and pictures! I have a pair of red foots about 10 and 5 years old. Living just s/w of Chicago 30 miles mine are indoors Oct thru may so jealous of being able to see them outside year round. They always look there best when the spend that time outdoors.