Sex-link is a term used to describe the sex-linking between sexes. When a male (in this case a Rhode Island Red or New Hampshire Red) male is crossed with a Rhode Island White or a White Plymouth Rock, the females will inherit the male red coloring, while the males will inherit the white coloring.
There will be some cross-coloring (the few white feathers on the females and the few red feathers on the males), but that coloring will not show up until they are much older and getting their feathers in.
The purpose of the sex-link is a dual purpose. It lays eggs VERY well, and because of their sex-linked colorations, are able to be sexed at day 1.
There are different colors, such as the red sex-link, gold sex-link and black sex-link. Hatcheries have different names for their sex-link...even though they are made from the same type of fowl. Some of the "strain" names are "Amber Sex-Links", "Gold Comets", "Red Comets" and "Black Stars". (There are several more strains out there, but this was just a run down.)
They look just like mine. Comets, stars, sex-linked are all the same from what I understand. They come in red, gold or black. Not sure if there are other colors. One of mine is almost all the light color, very pretty