This depends on the species--some species are easier to sex than others.
In most skinks, the male will have a larger, broader head, and larger tail base. This is something best seen when you have more than one animal for comparison. It is not possible sex newborns and juveniles.
one has a penis
I think by looking at it's scales.
If it has a spot on its bottom it's a boy if not a girl
size and color
there are only girl whip tail lizards
hi you tell a boy from a girl lizard by the thickness of the tail the boys tail are more thick than girls
usally the girl lizard is bigger than the boy
usaully the girl lizards are bigger than the boy.
sam, alex, bobby, robin
You do not tell if it is a boy or a girl by looking at it's color, the color changing green means the lizard is happy and if it is brown it means it is stressed.
No
Lizards have scales, and boys and girls usually have hair on their heads, and smooth skin.