I can't speak for barnevelders but with my Welsummers there is 100% difference in my males and females by markings. I have hatched them for some time and never not been able to tell a pullet from a roo. After I started breeding Welsummers I learned about the auto sexing here BYC from others on...
Yes by color markings around the eyes. Females have black markings like eyeliner around the eyes and a v shaped black mark right behind their eye. Males have none of these markings. Here is a pic of a male with no markings. Below is a link to a few more. Chick on far right is male, no...