Ok this is my observation of what chickens I have. They are all white leghorns. All of the young ones hatched from the older ones. They are NOT the pearl white leghorn breed, which I think has slightly different leg colorings and are not bred true to white leghorn standards.
MALES
My 2.5 month old cockerels don't have earlobes yet. Very yellow legs. Yellow as corn.
My 3 month old cockerels have earlobes are yellowish. Definately yellower than the feathers. Very yellow legs. Yellow as corn.
My 2 yr old rooster has yellow earlobes. They are very yellowish and huge. Yellow legs. Not as yellow as the cockerels but still yellow.
So it kinda looks like all of the males may have yellowish earlobes from the beginning.
FEMALES
My 2.5 month old pullets don't have earlobes yet. Very yellow legs.
My 3 month old pullets (pre-laying) all have white earlobes. Same shade/color of white as the feathers. Very yellow legs.
My 2 yr old Hens (all quit laying recently, some longer than others) have a mixture of earlobe colors. One has yellowish earlobes but the others are more white. The one that has yellowish earlobes, I think the comb has shrunk just enough to notice it isn't as big as it used to be, but barely noticable. All combs are still red. All legs are a very pale yellow.
So maybe you can judge who is laying by the earlobe color too, not sure.
Here is basically the difference in leg colors between my young chickens/chicks and the laying chickens.