A Black sexlink roo looks much like a Barred Rock with cuckoo barring and the hens are basically solid black with red in the hackle area.
A red sexlink rooster is white with red around the pyle areas. The hens are orangey or reddish with white around the hackles.
There is no trick. That's what sexlinked is-completely different looking sexes in that hybrid.
Note: Golden Sex Links and Red Sex Links are different creatures. But you are correct that "Red Star", "Red Sex Link", etc. are pretty interchangeable.