Simone is a tri-colored collie. Other collie colors include sable (like Lassie), white, and blue merle.
Male collies tend to have much larger manes, which is one reason all the collies that portrayed Lassie were male.
The thick undercoat at their necks was used during their jobs protecting livestock. If a wolf lunged at the dog's throat, they were likely to get a full mouth of hair and no contact with the skin at all. Likewise, they have a thick undercoating at the backs of their hind legs for the same reason.
Twice, one of my Jack Russells got out of the back yard and began roaming the neighborhood. Both times, Simone came to me immediately, pawed at me and ran back and forth to the door fretting, until I followed her. She led me to a window each time where I could see Eddie or Lucy running in the street. I opened a nearby door, called to them, and thankfully they came running straight back (with the bribe of a cookie). I then patched the hole under the fence where they'd made their escape.
